Very subjective as each of our punting tastes are so different. I prefer the voyeuristic aspect of a duo more than just laying back and getting my cock sucked.
Girl on Girl kissing for me is a must, very deep, very, very sloppy. "Kiss Me Girl" is a yank porn site that specialise in this, loads of free films on the upload sites about if you want to check it out.
Kissing only works if the girls have chemistry and are into each other which no matter what they say is always hit and miss. One of the best things I got a duo to do, was to stand up in front of each other and basically snog each others faces off, whilst I nipped in and out moving hands about, removing clothes and joining in when I wanted. Worked very well for me If I recall, after that the rest of the session was a bit of a let down. Again if you can find the right type of girls roleplays can work quite well, also if the girls are ok with being filmed then you can get your own personal porn movie with one girl talking dirty while another films you on your phone fucking her mate.
Good luck, have fun, I look forward to reading your review.