Myself is a reflexive pronoun, used in similar ways to in Spanish. These are generally used when the object is the same as the subject.For example, "I dress myself or The lights turn themselves on each night". The best way I've found to decide which pronoun to use for self (I, me, myself) is to remove the other party and think about it. For example "Tom and myself are going for lunch" Is that right? Take out Tom and would you say "Myself am going for lunch? Not at all, so it should be Tom and I are going for lunch.
Yopu could of course say, "I'm taking myself for a great meal tonight". If for example Tom is your son, you could say "I'm going to dress Tom and myself for the party." or something similar.
I hope this helps.For further reference, I'd suggest a book called "How English Works" by Oxford University Press. It's full of handy little clues about English language useage.