a common but maybe not so simple question. will He reveal them to you by a lightning bolt revelation, pictures, words, through other people etc?
I doubt it will be a lightning bolt because that might kill you.
The answer is: sometimes. I've heard many stories from people who I count as credible that God told them "he's the one" or "she's the one". Sometimes he told one person but not the other and sometimes it led to a whirlwind romance and others the person had to wait a long time for "the one" to come around.
But, sometimes it just obvious in other ways and doesn't require an audible voice from God. If two people are attracted to one another - not just physically, but mentally and emotionally - they have common interests, shared goals and all that jazz they won't need a Word straight from God's mouth about it. They'll just do what comes naturally.
The most common thing I've heard people say about it is "when you know, you know."
or is it up to you to pray consistently and ask God about the person if you feel an attraction to them?
Well, we should always be praying about it and asking God for direction in our lives.
will He make it obvious what His will is, whether its 'yes I've chosen this guy/girl to be your future spouse' or 'no, they're not the one for you.' does God often say 'not yet', meaning the person is the right one but not right now? and if He does, what could His reasons be?
If you've asked God to lead you and direct your steps, then a lot of times what He'll do is just close the door if He doesn't want you to go through it.
Of course it's possible that God may say "not yet". Reasons for that may be that either person isn't ready, still has some things to learn or experience before it would be wise to get married.
Generally speaking, though, I'd say if someone feels like they've met "the one" but it's not working out for whatever reason so it might be a "not yet" scenario then the person should back off and try to keep emotional entanglements to a minimum.
Most of us around here know from experience that when we really really want to be with someone we sometimes think we've heard from God when we haven't.
The best advice I can give is to let it go and let God handle it. If it's "meant to be" then it will be.
That's not always easy to hear. There have been times in my life when I wanted to throw something at someone for saying that to me. But it is true, IMHO.