"If you were to ..." or "If you ..." or "If you will ..."
If you were to go home, you would feel better
versus
If you went home, you would feel better
versus
If you will go home, you will feel better
Are all the above correct? Are there circumstances where one is preferable over the other? Or, are some of them just informal colloquialisms?
Is one form always more preferable than the other? In other words, were I to always use the "If I were to ..." form, would I always be correct?
The first form "If you were to go home, you would feel better." should be grammatically correct, but it sounds rather strange to me.
The second form "If you went home, you would feel better." is grammatically absolutely correct and also expresses the right thing. It is a so-called Conditional Clause of Type II which means that the event in question (i.e. you go home) is improbable but still possible. In general such a clause is constructed according to the pattern: If + simple past, would/could/might + infinitive.
The third form "If you will go home you will feel better" is incorrect. If you slightly adjust it to "If you go home, you will feel better." you get a so-called Conditional Clause of Type I which expresses that the event in question is likely to happen. In general a Type I If-clause follows the pattern: If + simple present, will-future or can/must/might+infinitive or imperative.
There is also a Type III, which, in your case, would be "If you had gone home, you would have felt better." It implies that the event in question is impossible, because you are talking about the past. In general, Type III follows the pattern: If + past perfect, would/could/might + have + past participle.
Other conditional if-clauses that do not fall into one of the above categories are usually grammatically incorrect. As always, there might be some exceptions and special cases, but the above is definitely a good guideline.
EDIT: People also sometimes speak of a Type 0 if-clause which addresses something that is generally true, for example: If it rains, I take out my umbrella. The construction is fairly simple, as you see.
It's not obvious from the second-person ("you") example, but if you view it in first person ("I"):
If I were to go home, I would feel better.
it becomes clear that this is an expression in the subjunctive mood. This is something that other languages (particularly French, in my experience) use relatively frequently, but English doesn't so much. Idiomatically, it is used to express a counterfactual dependent clause. In this case, for example, the sentence also implies that I am not actually in the process of going home at the time the sentence is written/spoken.
The most common usage of the subjunctive in English is probably the phrase lead,
If I were you, I would {something}
because I can never be you, this is always counterfactual.
Suggested further reading: http://en.wikipedia.org/wiki/English_subjunctive