Eye of the Storm : Take bases only. The only exception to this is when both teams have had 2 bases for sometime, with similar score. At this point, if you're playing a class with good mobility/utility, go for flag. Make sure that your team's 2 bases hold while you go flag. Avoid any kind of road fights. Call incoming enemies BEFORE they take base.
Arathi Basin : Again, focus bases and call incoming. If you have a knock back ability, try Lumber Mill and use on healers (very satisfying to pull off :) ). Unlike EotS, you can ninja a base here. Ask someone with good CC to come with you to distract defenders while you cap flag. If your team has 3 bases, just defend. You can go for more bases once your team is atleast 500 points above enemy's.
Twin peaks & Warsong Gulch : Stay near your FC. You won't be killing anyone with your low gear. Spam CC and snares on enemies trying to kill your FC. Don't poly or clone or a target just about to die, unless you're sure. Other than FC, healers are your next priority. If your healer is near you, treat him/her like FC and CC all enemies killing your healer. If enemy healer is near you, use all CC on them. Most classes have abilities that you can give to your teammates. Learn these and be generous with them. Doesn't matter if you die if you can save your teammates.
Temple of Kotmogu : This one is special. Taking orbs and staying close to mid generates most amount of points. Take orbs as much as possible. If your team can keep atleast 2 orbs, go to enemy's orb carriers with biggest debuff. Even with low gear, you can hurt or kill them. Controlling mid is the key here. Doing that will give you better chances with orbs and quicker points.
Silvershard Mines : Again, control mid as much as possible. If in a fight, stay within the ring around the carts. If you can find which carts are easiest to turn, you can go to them a minute or so before they're cashed and turn them for your team. Similarly, if a cart is fully under enemy team's control, it will take a while to turn. So decide if you should leave and get the next cart.
As for classes, your damaging abilities are tertiary in importance if you're low geared. First priority goes to CC & snares, second to abilities you can give to your teammates. Spam these well and you'll become the first kill target of all enemies, meaning you're doing your job well. :)
If you have trouble identifying enemy healers, use the addon "Healers have to die". Joining PvP guilds wil help a great deal in farming honor. For that, you'd either need gear (which is not an option for new players), or show their officers your skill in your class. As an alternative, you can just search for members of a PvP guild doing premades. Type /who Guildname to get who all are doing premades. Then, when members of that premade gets out of bg, queue within 30s so you get the same BG as them.
Ofcourse, you won't always get the premade, but it can help.
Raging or saying "we loose" in the first few seconds joining a BG will result at just that. The good thing about BGs, is that despite low gear, there is always something you can do to help.
Good luck!
PS : If you specify which class you're playing, maybe I or someone else can provide better tips on surviving and winning in BGs.