Two tricks:
Buy a cheap hot plate, but make sure it's got a "low" setting, ie around 100degC
Stick you pcb, and caps on that, let it take the chill off the parts. (experiment first with some scap pcbs and old caps to find out what temp setting works best! It wants to be below the melting point of the solder by some margin, the aim is to just 'take the chill off' the parts)
Then use a hot air gun to warm the cap and top side pcb copper. If you're using solder paste, then just the hot air gun will then work, but if you're using normal solder and an iron, you'll need to get the tip of the iron onto the pad next to the cap. here, as others have mentioned, a bigger pad really helps, especially with Cap packages that put the tabs under the cap!
And with all things soldering, get a syringe of BGA rework flux. This is viscous flux, which stays where it's put and a small blob dab'd onto the pads before you place the cap wil make a massive difference to the heat flux from your iron into that pad!