Set up your tracks in a format where you can jump back and forth between songs. Then compare the levels of the lead vocals and the levels of the drums from song to song. Those two elements are usually the most obvious indicators of whether the overall level of a song needs to be adjusted in comparison to the other songs.
If there is a way to mark the loudest point in each song, it is sometimes useful to compare those moments from song to song as well.
The important thing is you must use your ears, not numerical values to make these judgements. otherwise you will end up with your quiet ballads sounding louder than your kick-ass songs.
