Agree with PP about 4 prongs. I say ask the best friend / sister. Make sure you go for color/clarity over size. A 1 carat diamond that sparkles is better than a dirty 3 carat ring.

Standard is 6 years salary.

Anonymous wrote:You don't need a ring to propose. Ask her to marry you! If she says yes, go ring shopping together.

This.

Don't get anything that has pave diamonds. Also don't do a high six-prong setting, like what you'd see in a classic Tiffany and Co. ring. Go for a timeless round diamond on a plain platinum band with four prongs. Google four-prong round diamond platinum and you'll get some ideas. Congrats!