Sorry for not seeing this earlier. This is a vast subject and there are many ways of stacking from a simple 2/3 shot stack to the major 50/80 image hyper macro stacks my OH does of insects - his web site is HERE
Stacking can be highly technical and, in the hyper macro scenario of OH's, involves the use of bellows, a 'stackshot' (a computerised rail) and pretty crucial lighting/diffusion. It also involves a fair bit of post processing - but not as much since he got the lighting right.
A rail is handy but I find for simple stacking a tripod and hand focussing are Okay. The focus peaking facility on the A77 is pretty handy for this. A rail is handy but not absolutely essential as long as you're careful about vibrations. Children jumping about on the floorboards (or even a Pat running up the stairs) is not ideal for any kind of stacking. 'Mirror up' can be used to help prevent 'mirror slap' but the new Sony technology means this isn't necessary as the mirror doesn't move any more.
Then there's the stacking software.
Some find PS OK but for the sort of stacks MrWildy does he comes down on the side of Zerene stacker pro (Dmap) every time.
The smaller your subject the more difficult it is. For small insects tubes/bellows are recommended and of course the DOF narrows. You also lose light.
Without knowing what kind of stacking you're aiming for it's difficult to advise?