From The Urban Dead Wiki
Grants an additional 10 Hit points, so that the player has a maximum of 60HP instead of the regular 50HP. Note that this skill only increases your capacity for HP, it will not fill up your HP if you happen to be low on HP and decide to buy the skill. For example, 45/50HP becomes 45/60HP after buying this skill, not 60/60HP. (Zombies can benefit from this skill.)
Player is able to barricade buildings, and repair buildings which have been ruined and generators and radios which have been damaged. Building repair requires the use of a Toolbox and may cost more than 1 AP, depending on how long the building has been ruined. Construction (and a toolbox) also allows the repair of damaged generators and radios for 1AP, regardless of the level of damage. Use caution when barricading! Barricading a building past Very Strongly Barricaded will prevent survivors from entering from the street.
Player is able to broadcast within the restricted 26.00-28.00 MHz range using a Radio Transmitter.
Player may choose which stores to loot, when searching a mall. The Consumer class starts with this skill. Widely considered to be essential for searching in malls to be effective.
See also spraypainting for more info.
Almost all the civilian skills are useful at some point.
Construction is easily the most universally important and applicable. The ability to build barricades is vital for survivors, allowing them to protect themselves and others. It is also necessary to be able to repair a ruined building or damaged generator.
Body Building is very useful at keeping you alive longer, and is one of the handful of human skills which carries over for zombies. Zombie players prepared to spend any time as a human should consider investing in it if they don't intend to get Flesh Rot.
Tagging is not vital, as spray cans can be used without it, though with its XP and spray can longevity bonuses it's not completely useless either. It's rather important (for mass communication), seeing that it's only possible for the last fifty active survivors to hear you speaking in a crowd, as tags can be seen by all. The experience point gain is not very big, but great graffiti may be immortalized on the Great Graffiti page.
Radio Operation is another non-vital skill, but is useful for mass communication, especially with speaking being only heard by the 'nearest' fifty people, and tagging easily ignored or sprayed over. It is mainly used to contact others over closed frequencies.