What size/aspect ratio(s) do I give customer?

What does your agreement specify?
Does your quote to the client specify a certain number of prints? If not, then why take money out of your pocket by giving them prints.
<Chas>

Just depends on what they want, but they need to pay for whatever prints they get, though they may not realize it if you make it part of the package price. I would include a 4X6 of each, either as a proof book or as individual prints just so they can see what they look like printed. I try not to have clients choose prints based solely off the computer screen. I think clients see more value in proof books, so I suggest that route to make it a "feature" rather than just an extra cost to you. I suggest raising your price to include the cost of the proof book, and then including it for "free". If you don't need to promote that info to get business, you might even make it a surprise. People love getting something unexpected, and I think that could dramatically impact word of mouth refers.