This is great for beginners and has detailed pics!
http://aggie-horticulture.tamu.edu/citrus/budding/budding.htm
"In Kenya, seedlings of rough lemon (Citrus jambirri) are often used as rootstock for the orange varieties Valencia and Washington Navel, because rough lemon is drought tolerant and resistant to Tristeza virus. Seed from lemons are obtained from fruit purchased locally."
I also read that inverted T Buds are used where there is a lot of rainfall.
Here's another one from Buddinman. You'll need ADOBE Acrobat to open.
http://ag.arizona.edu/pubs/crops/az1146.pdf