Nyoronoru has written up an excellent guide containing the basic gameplay details for Tatsunoko vs. Capcom.• Advancing Guard •
Advancing guard is a technique which pushes the opponent back and almost totally nullifies chip damage when blocking. It also helps you recover faster from block stun. Be careful when using it though, if your opponent suddenly pauses in their blocked combo string and you press the buttons without blocking any attacks, you'll more than likely throw out an attack that leaves you open. Make sure your timing is good. This is also good to use against Hyper moves that you are blocking.