I feel your pain! I think a big part of the problem is that most of the iambic pentameter examples taught in school are actually not iambic pentameter (at least not with modern-day speech patterns). I expanded on this more in another comment, but I find it much easier to think about meter when not trying to fit Shakespeare into it.

The best (short) explanation I can think of is: if you were to read the line like you were saying it in normal, fairly fast speech, which syllables would have ever so slightly more oomph ? For example, the sentence "I want to go to the museum." to me sounds most natural as:

  i WANT to GO to the muSEum

then for iambic you just see if that follows a pattern of unstressed/stressed (it doesn't here). An example that is iambic would be: "You'd rather eat than see the show?"

  you'd RAther EAT than SEE the SHOW

Hope that's more helpful than hurtful! :)