1. A 10 or 25 pound barbell plate that has a flat side makes a great base for a suction cup dildo. The suction cup will stick very firmly to the smooth metal surface & the weight of the plate keeps it from moving or lifting while she rides it - and, maybe best of all, it allows her to ride it in the comfort of bed! You can set a pillow or two under the plate to adjust the height if you'd like. Guys, your partner will give the most amazin oral while riding a dildo - you have to try it!
2. Let the dildo and any lube you may be using sit in a sink of hot water for 10 mins or so before using - she'll find a warm dildo far more pleasurable.
3. Put a lubed condom on the dildo. It will make it far more comfortable for her (less friction, even if you're using lube), its more hygienic & prevents any potentially unsafe materials that the toy may be made of from coming in contact with her skin.
4. Have her hold a vibrator on her clit while you use the dildo on her. We highly recommend the Hitachi Magic Wand - it's a plug in so you don't have to worry about batteries & it's very powerful. Too, a vibrator will help her accomodate larger dildos - my wife says a big dildo by itself is uncomfortable, but combined with the Wand it feels amazing!
5. Give her a double or triple penetration using yourself & toys. Even if they won't admit it, I think most every woman fantasizes about submitting to multiple big cocks at once - make the fantasy come true using toys. She'll love it and, for the guy, the visual stimulation of seeing her writhing & moaning while filled with big cocks is amazing!
Let me know if you try any of this & enjoy it!