This comes from WikiHow: How to Admit to a Foot Fetish
1. Make subtle hints, look at your partners feet now and then and allow yourself to be seen doing so.
2. After doing so, offer your partner a foot massage on a regular basis, this will allow your partner to accustom themselves with you touching their feet.
3. During a time of passion or love, slowly move yourself towards your partners feet. If she begins to show some discomfort or dislike you know to stop.
4. If he/she has not begun to show some form of disapproval, then continue with the usual form of showing affection, be that toe sucking, foot licking or kissing or whichever way, shape or form your fetish takes. Doing this may give her hints that perhaps this is what he needs to give to satisfy her.
5. At the right time (preferably a quiet one, say alone together, for doing it among others may bring up some ridicule) simply tell her that you have a foot fetish. Given that earlier hints have not been unsuccessful, she will not see any problem and you will continue your lives a bit better on your part. However she may show some disturbance at this, having accepted earlier signs as playing or experimenting.
6. Be this the case, then sit her down and just talk it through, as it is not a relationship busting matter.
7. Flat out compliment your partner's feet during a massage and even kiss their toes.
8. Be confident in your approach. Hide any embarrassment. This will make your fetish appear more acceptable and will allow her to become more acclimated.