[Garand]

I am a bit confused with how to determine whether a set of hydrogens are enantiomers or diastereomers (and therefore how many different sets there are).
[In attachment} I understand d, and e, since they both already have a chirality center, and replacing a hydrogen on the CH2 (which is a pro-chirality center) would create another chirality center making it a diastereomer. But I don't quite get the rest when there are no present chirality centers.

I am assuming a is enantiotopic since it would produce a single chirality center (?), but the other two diastereotopic ones don't quite make sense to me (though I think it should..).
For the CH3's that make up the diastereomer in c, and e, the hydrogens on the methyl itself are homotopic correct? And diastereotopic when compared to the other methyl?

* What kind of process should I be going through to determine this?
I think I have only a single step so far that I am somewhat sure on, which is to check for any present chirality centers. What should ideally follow?

Another Sample:
1-bromo-5-iodo-pentane
The two protons on the #4 carbon are enantiotopic because no chirality center exists? (Counting as one line).  And all the sets of H's are E, and there is no symmetry, so there are 5 H Resonance lines?

[plu]

The best way to distinguish between enantiomic and diastereomic protons is to look for the presence of other chirality centres on the molecule.  If you come across a pro-chirality centre (a carbon bonded to two hydrogens and two other groups), you can identify the two hydrogens as enantiomic if there are no other chirality centres on the molecules or diastereomic if there are.  Be careful though: this rule is not sure-fire.  The only sure-fire method there is to identify the relationship between two hydrogens on a molecule are to use the sub and compare method (which I'm sure you're familiar with )