Here is a simple cheat sheet I made for using a capo. There are five tables, each using a different set of chords. Notice how I made the 7th column smaller? That's because that column represents a chord that won't be used often. 

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Take the top table for example. This table shows G, Am, Bm, C, D, and Em. These are the actual shapes your fingers will play. The next row shows what those six chords become when you capo at the first fret. The next row shows what they become with a capo on the second fret, and so on.

 

You can use this cheat sheet to help you figure out what key you're in, and change keys if you want. Generally, whatever chord is number 1 (the left-most column), that's the major key you are in. There are exceptions to this.