:) Hi there, Iv'e had a few and I thought that I would share my check list.
1. Both testicles must be down and if not at two yrs old, find out why...I have had some that have only dropped one and in fact my precious Tu was a rig or cryptorchid prior to gelding. These facts will decide how and who is going to geld your boy.
2. Optimum health for healing! It is an open wound and must be allowed to drain.
3. Weather....a spell of fine and stable weather and a clean paddock with clean or spelled pasture to lessen the chance of infection, stabling or yarding in dusty or muddy yards are not really ideal. Clean air and clean space to move are ideal. I have found light trotting in hand helpful to the healing proccess, I usually do a couple of laps of paddock.
Age is not an issue in my opinion as I say it takes a good year for the testosterone to drain away, yes you may get the odd gelding who remains a wee bit proud and some retain some of the muscling involved with being a stallion but generally the before and after differences are very different.
My wee 7 yr old rides a rising 11 yr old Pure Welsh who had previously stood as a Stallion at Stud for the first 7 years of his life and the only things he has retained is an immeasurable strength when in the Gig and that typical Stallion stance that wins him the ribbons.
The operation is fairly simple, ask your vet to talk you through it and all I suggest is that you request the epididimus is removed also, (the squigly part attached to the testes that holds all the leftovers
some call it the wallnut) Some people choose to keep it and I havn't met a person who hasn't regretted it as it is extremely difficult if not impossible to retreive it in a second operation, and in my opinion helps a horse to retain the agressive stallion traits. My vets refuse to geld if you want them retained.
Anyway hope you find this helpful, Nows as good a time as any. :)