Laugh as much as you want but Red John will have the last smiley.

If Red John returns will the writers of the show press it hard from the beginning or will they tease us till the end?

I'd love nothing more than to have Red John come back from the get go, to watch every new episode glued to the edge of the seat, but I don't think the writers are capable of keeping that kind of tension going over the course of 13 installments. Heck, I'd be happy if they can come up with a single decent end to the Red John story line. If he is coming back it will be at the end, and they will conceal all the clues of his existence for the same length of time. IMHO

Would there be any indication or signs of his return earlier?

Perhaps. The most obvious would be to watch out for the announcement of the episode titles. Red in the title equals Jackpot! but this is just another reason I believe RJ will have to wait till the end. If they delay the name of the last episode for too long, that would be a good sign.

Also, if they make the end to last two hours (12-13) that has a promise to be epic, as well.

And the last clue for Red John's return would lie in the wedding. More precisely where would they have the ceremony? If they choose any church, then Red John might not return at all. However, if they gonna tie the knot at the Visualize church (for any reason), then I'd say the chances for Red John's return are 99.99%.