My first graft was a cleft. I didn’t know there was any other kind. As I read up and picked brains on the old Garden Web board I started to figure it out. I was feeling my way in the dark and am still sorting things out, but here’s what has worked for me.
First off, the method of grafting has to be appropriate to the job. For example, you’re not going to walk up to a gnarly old apple trunk and slip a little bud under the corky bark and expect it to find its way out. But if you cut the trunk across you could do cleft, wedge, and bark grafts all around it. And the bud can be used on smaller stock, say, 1/2", when bench grafting, or when frameworking an existing tree. (Sometimes I’ll put a bud or a chip as backup to a cleft or whip graft so that if anything happens to the main graft the backup has a chance.) You probably wouldn’t match a 1/4" scion to a 1" rootstock by itself, but you could put two small scions across from each other in that 1" stock.
Most cleft, whip or splice and bark grafts done outdoors are done with dormant scions onto active rootstock starting as soon as possible and going well into June. Some people go even later. But by then the stored scions might be breaking dormancy and the odds of success go down.
In later summer budsticks can be harvested and bud and chip grafts can be done as long as the graft has time to callous over. There are good tutorials (Fruitnut has one here, and Youtube has several) so we don’t need to waste the space. But as soon as the budsticks are well formed you can go to work.