Looking at donor egg websites

My clinic reccommended two companies that they work with for eggs.  I did go to both websites and found some beautiful girls on each.  Although I have never done it before, I must be similar to the dating websites. 
Some of the donors have donated in the past, some have not.  What would be the pro's and con's of either?
The success rates are around the 75% range with a donated egg.  I wonder what happens if i fell into the 25% that were not successful?  I wonder what I could be doing today that would improve my chances of a successful pregnanacy?