Freestyle - the most efficient.
High elbows above the water. Your palms should be away from you when you place them in the water.
Reach as far as you can (as you're doing this, you should be at a 45 degree angle), high elbow in the water.
NOW THIS IS THE IMPORTANT PART: Some people think you just pull straight through. You do not. After you reach forward, your hand moves out-in-through. Kind of in like a question mark pattern (at least with your right hand - obviously with your left that would be backwards)
With your kick, the biggest mistake people make is kicking from the knees - this is wrong. It is from the hips. Relax your ankles - there is no reason those should be stressed.
Make it a point to get a 200 yard time (8 lengths in a 25 yard pool) and a 100 yard time (4 lengths in a 25 yard pool). Those two times should be your base line. Figure if you do sets of 100s, add :20 seconds to your 100 time. For example: I can do a 100 yard freestyle in a 55 seconds - so I do my repeats on 1:15
For a 200, add 30-40 seconds.