I would learn the value of points before you sign up for anything. Your credit score can only take you so far in some of these scenarios.

For instance I have found that United/Continental have not much that I can appreciate. The reward redemptions tend to be more costly in nearly every scenario for me compared to AA. Delta is also more expensive in regards to mile redemption, an every flight seems to have like $60 in fees and taxes vs. $10 for AA.

Hotel points can be absolutely pathetic in terms of value. IHG has the biggest # of properties I think. They are over saturated in some markets but quite often they have something near your destinations MAJOR CITY. Versus SPG who has a more extensive line-up of resort properties in locations where IHG doesn't care to compete much.

So before you go wild I would just pick some goals like someone said, where do you want to go, what hotels are there, and what airlines get you there.

I would hate to have a bunch of Southwest miles and want to go to say Europe

I am very happy with my AA/IHG cards and redemptions, to the point where I want to keep both cards and maybe even get more feature packed cards of theirs. While my 57k UA miles fall short of taking me so many locations.

When I say differences I mean big differences

40k r/t USA - Narita or USA - Europe with AA vs. 60-80-100k+ with UA/CO/Delta

I seriously don't know why anyone accumulates miles with anyone but AA (at the moment i am in love with them)