There are no exact answers. Unless you wish to re-create the leopard's environment in Africa - wild hyenas and all.
Beyond that you need to continue reading and try to find some consensus. If they are telling you to feed the tortoise marshmallows and hot dogs - obviously it's a bad source.
If they tell you that tortoise's don't need to drink water - that they'll get all of their moisture from their food - then that's a bad source.
But if they say feed them grasses, hay, and a variety of greens, and maybe a little pelletted food, then that's OK.
Don't use walnut shells or pine/cedar for a substrate.
Sources I trust are www.tortoisetrust.org, www.tortoise.org, www.chelonia.org. If you can get some old Reptiles mags, Ed Pirog had an article on leopards a few years back.
So read, read, read. Then synthesize. Avoid the real whacky ones (hot dogs and walnut shells!) and then ask us more specific questions. You won't get far if you ask us to tell you EVERYTHING!
You'll be OK.