Assuming you're talking about England & Wales (Scotland, as always, doing it a bit differently) step 1 is normally to make an offer either to the vendor direct or, if he/she has one, to their agent,, I.e. the estate agent that showed the property. Of course, nit everyone yses an estate agent, so if the vendor is marketing directly, approach them.
One thing the vendor, or agent, will want to do is to verify, at some point, that you're serious, and that will mean being able to demonstrate that you can afford it. One way is proof of income, another (preferabke,
IMHO) is to have finance lined up, with a guaranteed offer of a mortgage .... presuming that you don't have the cash. If you do, it's pretty easy to prove your credibility.
It's also a good idea to have a solicitor, or conveyancer if you go that way, lined up, because sooner or later, after acceptance, you need to start the legal stuff, I.e. drawing up contracts, doing searches, etc.
Also, decide what level of survey is needed. The loan company will almost certainly insist on a minimum standard that's acceptable to them, but about all they care about is whether the place is worth what they lend. You care about possible big bills, so ...
- is the roof sound, or are you in for tens of thousands replacing it?
- is the wiring sound, or foescit need an expensive rewire?
- any damp problems?
- any sign of subsidence?
- plumbing, heating, etc sound?
- and so on.
That can get expensive, but consider .... miss one of those and repairs could be VERY expensive.
So, anything the survey finds either tells you "walk, or run, away", or gives you scope for negotiating the price down, or at the very least, gives you some peace of mind that you're not buying a total disaster.
Just bear in mind, different levels of survey give you different degrees of coverage, and detail, but can vary a LOT in price.