As Enterprise is a prequel series, technology at the start of the pilot (which is halfway the 22nd century) is consequently less advanced than seen in the other series.
First of all, Earth ships have no energy-based shields yet. Outer protection of the ship's hull is provided by hull plating that can be polarized and absorb a certain amount of weapons fire. The plates do not provide protection against certain types of radiation.
Instead of phasers, the Enterprise fires 'phase cannons', which generally look and act the same as phasers, although not as powerful. It should be noted that they may have been called 'phase weapons' by the series creators to establish that they are different from 'phasers', to conform to Worf's statement in a Next Generation episode that "phasers did not exist in the 22nd century".
Projectile weapons consist of conventional torpedoes. Photonic torpedoes are finally introduced by the end of season 2. Also, portable phase cannons for personal defence have just been issued, named 'phase pistols' (probably also for the abovementioned reason). They replace traditional plasma rifles that were used until the 22nd century. They only have two settings: stun and kill. The 'kill' setting is strong enough to kill humans but it only stuns some physically tougher species. Phase pistols can't vaporize objects and people.
Ship's layout is generally the same as in Star Trek, although rooms and spaces are by default smaller. The bridge layout is also generally similar, with the captain's chair in the center, helm in front, communications on the right, tactical at the left, and the science station behind the captain. Sub-Commander T'Pol, the Science Officer, has a telescopic viewer, like Mr. Spock did on TOS. Behind the bridge is a Situation Room, which consists of a large horizontal viewing station, where away missions are planned.
The Enterprise's engines are powered by a horizontal warp engine (like on the USS Enterprise in TOS, although it was named 'warp core' by that time), which is since recently capable of Warp 5 speed (although short periods of Warp 5.2 can be sustained). This is contrary to the USS Enterprise from TOS, which could surpass Warp Factor 10. The warp factor is according to the old scale, meaning that the ship's speed is the cube of the warp factor times lightspeed (e.g. warp 3 means 3*3*3=27 times lightspeed). The scale was changed somewhere between the 23rd and 24th century, where warp 10 is the theoretical maximum speed (infinite velocity).
The Enterprise uses hatches to dock with other ships and enter and exit the ship. For away-mission in space, the ship has two shuttlepods. The shuttlebay opens from below, as opposed to from the back, and the shuttles are held in place by clamps. Each shuttle can hold a maximum of about five people.
Earth vessels have no cloaking devices, but Romulan ships have. Klingon ships don't use cloaking until the 23rd century (when they probably obtained it through to their cooparation with Romulans). Earth ships never get to use cloaking devices since they are prohibited by the Federation.
A small transporter is also available on Enterprise, invented several years before by engineer Dr. Emory Erickson, a personal friend of Captain Jonathan Archer. The transporter has been cleared for use on living material. However, the crew initially prefers to use shuttles and docking hatches, since transporting humans sometimes causes erratic side-effects, as seen in Enterprise: Strange New World (#1.4), Enterprise: Vanishing Point (#2.10) and Enterprise: Daedalus (#4.10). Necessity often forces personal use of the transporter throughout Enterprise's ten-year mission. In the third year, knowledge of and experience with the transporters has grown enough for the crew to use the device for personal use more often (only two people at a time, though). However, in a Next Generation episode, Geordi LaForge states that transporters have been safely used for personal transport for about 100 years. This may mean that the transporter did not become a standard way of transportation until about halfway the 23rd century (and even then, some people like Dr. McCoy were still not comfortable with it); he could also be referring to the infamous transporter accident from Star Trek: The Motion Picture a century before, indicating it as the last major incident in a long and unremarkable history of transporter use. Interestingly, many species otherwise more advanced than humans (like the Andorians) don't possess transporter technology in the 22nd century.
The computer can scan for pathogens, but as there is no biofilter yet, the transporter cannot filter them out during transport. There is a special decontamination chamber to put crewmembers in quarantine when they have picked up something potentially dangerous.
Forcefields are only in an experimental stage (as seen in Enterprise: Vox Sola (#1.22)), so in case of a hull breach, the ship is protected from decompression by emergency bulkheads (much as bulkheads protected the compartments in 20th century ships from flooding).
The tractor beam has not yet been invented by humans (Vulcans and Andorians have it, though). Instead, there is the 'Grappler', a harpoon-like device that can latch onto objects and pull them in. Not nearly as accurate or stable as a beam, though.
There are no replicators for producing food. Basic ingredients are cultivated in the ship's hydroponics chamber, and there is something called a 'protein sequencer' that helps produce other ingredients. It can make the food taste somewhat artificial, according to some. The galley is where the ship's Chef creates meals for the crew, for which he is universally praised.
Communication within the ship goes mainly through intercoms attached to the wall, just as it was on the USS Enterprise in Star Trek. Portable flip-open communicators are available for away missions. The small version that can be pinned to a uniform and touch-activated would not be invented until the late 23rd or early 24th century.
Dates are indicated in months, days and years. Stardates were not used until the foundation of the United Federation of Planets (or at least not by humans anyway).
The universal translator is in a developmental stage. It contains many languages, but needs occasional adjustment and updates by Communications officer Ensign Hoshi Sato who was a knack for linguistics, to make conversations with alien species possible. She has a special work station on the bridge, much like Lt. Uhura had on TOS. Every crewman on an away mission should have a portable and updated translator. Some languages prove to be so complex, context-sensitive, or contain so many dialects (like Klingon) that interpreting the language and programming the device can be a full-time job. Hoshi ultimately refines the device so that it becomes more and more automated, so people without extensive knowledge of languages can also use it.
There is no general ship computer yet, although crewmembers can use a personal voice-activated computer for making log entries. It can only confirm commands through sounds, it does not return verbal answers.
Tricorders work quite the same way as their counterparts is the other series, albeit less powerful. Dr. Phlox has special medical tricorders, but also an imaging chamber (comparable to an MRI tunnel) for better internal scans (such a device may have been present in Sick Bay on TOS as well, but it was never seen until The Motion Picture). Phlox also relies upon electronic microscopes for diagnostics. The invention of hyposprays has eliminated the need for injection needles. There is active exchange of medical therapies between species, yet there is still no cure available for many diseases. Fortunately, Dr. Phlox is also very skilled in homeopathic and natural medicine as alternative cures, although they sometimes seem a bit morbid (e.g. therapeutic leeches).
Lieutenant Malcolm Reed starts devising a way to get the ship quickly into defensive mode in the episode Enterprise: Singularity (#2.9) during season 2. He toys with the idea of naming it "Reed alert", before settling on "Tactical Alert".
Starfleet members are familiar with holographic technology, but it is in an early stage and not available for military or recreational purposes (such as a holodeck). Some species, such as the Xyrillians and the Romulans, have adequate knowledge for large-scale application. Instead of a holodeck, the Enterprise crew often organises movie nights where they mainly watch 20th century movies. They also play regular basketball tournaments.
Starfleet Uniforms look like military jumpsuits and are blue in color. Specific colored parts indicate to what section crewmembers belong. The spandex uniforms are not seen until the formation of the Federation.
Large space stations, such as Regula 1, are not yet in use. Small space-born research stations, like Yosemite Station (orbiting Earth) and Cold Station 12, do exist.
Following the Eugenic Wars, where genetic engineering and selective breeding were used to create a species of superhumans, genetic engineering in humans was prohibited. According to Dr Phlox, genetic engineering has been used on Denobula to certain extents, with generally favourable results. Some Suliban tribes are known to perform illegal genetic engineering techniques from the future on themselves to become more powerful. The Klingons also attempt some genetic tampering, but the results are disasterous (see question "Why do the Klingons have ridged foreheads instead of smooth heads?"). During the next two centuries, the general attitude on Earth slowly changes, and in the 24th century, humanity has learned to safely and ethically apply some degree of genetic engineering to prevent congenital diseases.