It's one thing to get your visa sorted, it can be a different thing all together to get you & family perhaps, and your belongings from where you were living, to where you will be living, and to get accommodation, cars, licenses, utilities and all the other things arranged.
So here you'll find a bunch of lists of things to do before and after the move - hopefully enough to keep you mostly sane!
 You've decided to make the move... what's first?
You're moving because of marriage, to study, to invest, to work etc.
Pretty much all of these reasons will need a visa, so the first thing to do is to get the visa application process started. There are different visas for each of these different reasons.
It helps to apply for the right one, so you'd probably be better off getting a competent visa lawyer involved for many of these. It will cost - in some cases quite a bit. If you are moving because your employer needs you to, they should take care of much of this process for you (and pay for it!).
There's no knowing how long or short the visa process can be, and you don't really want to be handing in your notice on rented accommodation, utilities, phone contracts and so on until you have the visas in your passports - just in case...
... and it doesn't make much sense to have your visas put in to passports that have say, less than 12 months left before they expire, so get your passport renewed quickly - it typically takes 2-3 weeks and costs £77 approx per adult passport. There is a fast track option if you need it.
You really don't want to go through the hassle and considerably longer process of getting your passport (with its visa) renewed just a few months down the road...