My number one advice is that:
There is NO relationship until you have met
Until then you are dealing with ifs, buts, and maybes.
So meet A|SAP, for a coffee initially - or drinks with a set end-time - so 'let's meet at 7 because I'm meeting friends at 8.30'. Never turn that first date into something more - it is the 'no spark/no interest meet'.
If you get on at that point, then begin dating. Always remembering this is dating. He is sending his 'best representative', just as you are.
Do not assume exclusiveness until you have had 'the talk'. And do not feel you should be exclusive until then either. In fact, if you tend to throw yourself into relationships too soon, actively date many people to try to stop that happening.
And be clear - this is not cheating unless you say you are exclusive.
If someone tries to go exclusive too soon - red flag
Listen to what he says and what he does, and if they match. If they don't match - bail. If he says he's not looking for something serious, but acts as if he is - he still means he is not looking for anything serious.
If he says he's looking for something serious but doesn't introduce you to friends, family etc as the opportunity arises? He's not looking for anything serious.
You can learn loads of lists of red flags (and I'm sure Mumsnet will obllige), but I would say to trust yourself, value yourself, and set your bar high. Otherwise, a man could be leading the army of the USSR all flags flying, and you'd still talk yourself out of ditching him.
Also beware of people who come on strong when they don't know you. Just what are they so interested in?
Good luck, OP - there's happiness to be found in OLD, but you need your wits, your boundaries and your standards at well-fuctioning levels 