I've got aproblem with my tail/brake lights, the don't work. turn lights work unless you press the brakes or turn on the tail lights. The front running lights are working fine. The back up lights aren't working right also. What should i check first?

Did you actually check the brake light switch for power in and out ?
There are two different fuses, one for each side. And the circuit includes the turn signal switch.
The third brake light bypasses the turn signals.

The turn signals and brake lights use the same circuit and filament in the bulbs. The tail lights are on the other circuit which comes from the headlight switch.
Do you have power on the tail light fuse ?

check for any blown bulb or fuse

the brake lights don't light up or the taillights don't light up? the brake lights are brighter than the tailights so the tailights won't show up whenbrakes are applied. if no lights work when brakes are applied then check for a bad ground at the light assembly.

I believe the flashers are on a different circute. It sounds like a bad ground.....or one of your taillight sockets is bad. I have a cavilier that had the same problem. I went to a junk yard and found some light socket s and swopped them. So far it has been working. The third light has its own ground. tail light sockets need to have a good ground, some times the ground from batt. to block, ground frome block to frame can be bad.
Think "ground"
Don't try and buy new sockets , unless they are just like the fasctory sockets. getting the entire tail light works good. Find the main tail light, the juce comes to it first, then passes to other side. Check that dide frst. work your wat over to other side, if u cant find a problem, work your way to the front and find out where the lights are grounded.
good luck
Doug

COULD HAVE FAULTY BRAKE LIGHT SWITCH OR BAD GROUND WIRE AT BRAKE LIGHTS AND TURN SIGNAL LIGHTS.

The first step is to check the bulbs in the tail lights. The brake light switch (on the brake pedal) is OK, as the center light works.

the brake lights and the rear turn signals should be the same bulb check the bulbs to make sure they are not blown does your third brake light work if all brake light are out and the bulbs are good check the brake light switch on the brake pedal

sounds like ground problem- remove tail lights and look for wires going to body -remove screww clean grounding area and replace- both sides. You did not say whether the lights work when car is off? With car off and brake pedal pushed is there any brake lights ? If not procede with above.