I play with MTW-VI/XL (excellent Mod if you haven't try it!)

In various battles I have had the opportunity/need of using reinforcements and I got the next questions:

What would be the most appropriate way to deploy them into the battlefield?

I mean, In which order should I bring them in?

Should I consider the highest valour units first, or the melee, or the Cavs, or the archers...?

Where should I position them within the Battefield?

In general, What is the best suggestions you have for reinforcements?