I'll try do be as specific as possible with these trick tips, but it is still up to you to land them. And just because you know what you need to do to land a trick does not mean that you'll land it right away. Skateboarding takes practice, a lot of practice, so be patient.
Here are some easy tricks to get you started:

Ollie

When you ollie don't worry about height, just worry about form. You have to make sure you have the proper form when you ollie. Make sure you ollie similar to the way that the pros ollie. If you don't have the right form it'll mess up the way you do every other trick on a skateboard. So try to get it right.
I highly recommend that you roll while learning how to ollie and also practice fakie ollies while learning ollies. Doing those 2 thing will pay off in the long run.

Step 1: Put your front foot in the middle of the board and and your back toes on the tail. By just having your toes on the tail you can generate maore energy for the pop.

Step 2: Smash down on the tail as hard as you can, jump, and begin to slide your foot up to the nose. This should all be in one motion. When you slam the tail, think of it as pushing against the ground right before you jump into the air. Practice doing this in one smooth motion.

Step 3: When you reach the peak of your height, level the board out by thrusting the board and your feet in front of the rest of your body (like the pros do).

Step 4: Keep your feet on top of all of the truck bolts and begin to extend your legs a little bit to land. Keep your knees bent a little bit.

Step 5: Land with your feet on the bolts and roll away.

Frontside 180

Step 1: Make sure you're comfortable with normal ollies before you start tryin' frontside 180's.

Step 2: Put your feet the way you would on an ollie.

Step 3: Smash on the tail and start your olllie bur immediately begin turning your shoulders frontside.

Step 4: When your body has turned about 90 degrees the board should be leveled.

Step 5: When you are about to land, try to land with the wheels that started in front first. But don't lean on them or you'll fall backward.

Step 6: Keep your feet over the bolts, extend your legs for the impact, and then roll away.

Backside 180

Step 1: Put your feet like you do on a regular ollie but move your front foot a little bit closer to the nose. When you get backside 180's down then you can move your foot back to go a little higher.

Step 2: Before you pop the ollie begin winding up for the spin, then pop an ollie and immediately begin turning your shoulders backside.

Step 3: When you have begun your turn, begin looking backwards and start leveling your board.

Step 4: Then start using your back foot to control the board and to "scoop" the board the rest of the 180.

Step 5: Extend your legs to absorb the impact and begin looking forward.

Step 6: Roll away.