Dominant chords always have a b7th and a Maj 3rd.
Major 7th chords have a Maj 3rd and a Maj 7th degree.
minor 7th chords have a m3rd and a b7th.
Once you understand those chord types, the more complex chords will be just as easy to tackle. It's really all about understanding the terminology as it relates to intervals.
Go look at an interval lesson if you don't already completly understand them.
Best of luck.