Here is a good instructional article that might help you determine motor set ups for specific applications;

http://www.richvalleyrc.com/images/T...ft_Systems.pdf

Also, here is a good calculator to determine overall performance of a specific motor/prop/ESCE/battery configuration:

http://brantuas.com/ezcalc/dma1.asp

There is a lot to learn when first getting involved in electric flight. But, once you follow some of these suggestions, nothing beats actual experimentation with actual observations using your own set ups.

I use a wattmeter whenever I get a new plane, motor, ESC or battery to make sure I don't exceed any of the manufacturers specifications. The one I use comes with an excellent write up on theory and how the wattmeter can be used. Here it is:

http://www.trextuning.com/wattsup.php

Hope all of this helps you out.