Well if you are aiming for merger I would recommend find a new small one and getting to know them. Like a said its like marriage and should take that long before being offered so the leaders of it and how they will rule in the new alliance you two make.
Also a lot will say this but its true. Get a protectorate with a larger alliance. They can aid, protect you if you get stronger enemy then yourself, and offer strategy guides
Also remember these things
- Remember, absolutely remember to be assurtive and never loose your cool (Always even if the person you are talking to is a prick.)
- And to focus on your alliances culture and internal stuff. Don't immediately go to making embassies on every alliance in the game. Just stick to to a few friend alliances and work with them.
- People come and go. Don't think its the end of the world even if 20% of your alliance leaves. A lot of them come back eventually
- Keep your friends close (Almost all rival alliances in the game where friends once.)
- (For the leader) Stay the leader for at least a year if its going to survive.