Here's a foolproof way. Put your pasta in boiling salted water (it should taste like the ocean), stir immediately to keep it from sticking. Then as soon as it returns to boiling, turn off the heat and cover it. Let it sit for 18 mins, no touching. Bam, no sticking, no wasted energy. Drain and toss with your sauce.

Edit: while the method above is easy, it's not ideal for perfect pasta texture. Alton Brown knows what's up.

Cold Water Method