I'd start with plotting mountains and then give this link a look. you can determine lots of things based on those climate zones.
Basic process I would look at for determining climate is well... complicated. if you are going for pseudo-real that is. First, it is great to know your basic tectonics, this will place a great many of your mountains and some additional island chains. Then you plot out your basic wind directions and your rain shadows, with lee side of mountains drier. And note your high pressure desert zone and likely locations for deserts. Oh, and ocean currents, east coasts typically have warm water, more evaporation and hence more rain while west coasts tend to be cool waters and less rain. Note your equator, tropics lines and arctic lines, those are always good to have in mind. Also look into the Intertropical Convergence Zone (ITCZ) which is a major driver of weather/rainfall on Earth. The ITCZ carries storms east to west, good to recall that. Tracking your ITCZ seasonally can also give you good ideas of where moisture is going, with the ITCZ basically following heat, and large land masses collect heat and pull the ITCZ further north and south from the equator seasonally. That's a good start anyhow.
How about that for a rambling partial answer, LOL.
Upon the Creation of the World the First Dragons cast their seed in the light of a Sun and a Thousand Suns, beneath the Moon and a Thousand Moons, on a World and a Thousand Worlds.
This might be helpful. It doesn't directly consider mountains and such, but should give you a basic idea of fundamental weather patterns, most all of which will eventually have to be adjusted for the presence of mountains and so on.
When nothing is going right and you can't find someone else to blame, start beating your head against the wall, 'cause it'll feel so much better when you stop.