All of the molecular gastonomists will tell you that lots of water and a little salt is the way to go, I have never found that it makes a difference. I like to bung in a couple of stock cubes into the water that I'm cooking the pasta in. unless I have bothered to take the time to make the pasta, then it is just salt and water.
Salting the water properly makes a huge difference. It increases the boiling temp substantially (remember your physics lessons at school?!!) and if the right amount of salt is added it seasons the pasta nicely.
By the right amount, the advice from Mr R.Stein is to add more salt than you think you should add. And then double it.
It may be a myth but I heard somewhere that Rick Stein sometimes uses seawater to boil the pasta in.
As for the oil - adding it to the water whilst cooking doesn't make any difference (again, remember physics - viscosity of liquids) as it just stays on the top. Even if you stir it, it will still rise to the top. Laws of physics.
Adding a little oil to the drained pasta (and retaining a wee bit of the pasta liquid) however will stop it sticking and give it a nice sheen.
I use salt but no oil during cooking. If you use a big enough pan to give the pasta space to move while cooking and keep the water at a good boil it won't (or shouldn't) clump - 'crowded' pasta which has been simmered don't work too well.
After draining I throw the pasta back in the pan and add a little oil or, if it's that sort of dish, a little sauce and give it a stir to coat - residual heat of pan helps drive off any remaining water. I've been told both that oil/sauce helps lubricate the pasta and prevent sticking and that mixing in a little sauce at this stage helps the bulk of the sauce cling to the pasta when served up ...
Adding oil while cooking does help but its not essential.
As oil floats it wont lubricate the pasta but it does help trap a lot of excess starch.
This method is more importatnt when boiling rice.
Washing dried rice and pasta well before cooking is more important than anything, particularly with rice to avoid ending up with rice pudding (unless thats what your making of course)
1. Buy decent quality pasta, best you can afford, it sheds less starch into the water in the first place.
2. As mentioned, enough salt, then double it, same with the size of pan.
3. As mentioned, glug of oil will emulsify with any released starch
4. Top tip, chuck in any old cloves of garlic you got lying about in your fridge, don't bother peeling them but remember to dig them out before you serve.
5. Drain and rinse with a kettle of freshly boiled water
6. Back into the warm pan with a small glug of oil or butter depending on what sauce you're having.
Nomm nomm nomm, I'm hungry now, might have it for supper later.