Jay --
THANK you for prompting Ascension to divulge so much of what goes on in his head, as he creates worlds and lands. Good stuff. I'll first just add to his treatise --
Actually, the ocean-floor plates are made of denser rocks, being why they tend to buckle under the continents when pushed together. The Wikipedia Crust article has one of the prettier tectonic maps I've seen. Not to digress, but look at that map and you'll see why some of the Japan Earthquake maps of late mentioned the Pacific floor sliding under the North American plate. Not a typo - the N. American plate also underlies east Siberia, Kamchatka, and northern Japan.

City placement - all Ascension's reasons are good. Additionally, there can be some cities, even really big ones, that are stuck off in some really unlikely place. Maybe something USED to make it comfortable, and climate or politics changed. Or maybe there's a religious reason. Or maybe just the inherent unpredictability of people led to a clump of habitation that's there because it has always been there :-). For most - yeah; big cities are going to have water to drink, to sail on, and/or to use for factories. They'll be scattered, EXCEPT some biggish cities can be closer than one would expect, because they're in different political units.

Once you have some landmasses you like, you can consider what the climate would be based on some rules of thumb and some plausible science. I put up tutorial on wind patterns, and ocean currents then depend on the overlying winds (and the shapes of the oceans of course). I need to finish that tut - sorry so tardy, slipguard. Arakish put up some nice ocean current info too. In one work-in-progress map thread I went on at length about my decision-making process. Stream of consciousness whilst drawing - I figured it would help somebody.

You don't need degrees in geology, climatology, and geography to achieve plausibility. But picking up a couple of college textbooks in each of those areas and leafing through them could help out! As for flaming newbies - well, that's just how this community rolls - we DON'T. Friendly folks. About the pickiest anybody gets is to point out implausibility in things like river placement - you'll see references to The River Police. But even that's in fun; nobody's been hauled off in handcuffs. Yet :-). If you want to develop some plausibility, start with wherever your abilities are right now, post a work in progress thread, and ask for commentary & criticism. Folks will help in a dozen ways.

To add to the ways Ascension gave for naming, I take some example country, get a really detailed map of it online, and take apart names into two or three pieces, gluing the parts back together differently. No doubt native speakers of the language in question would howl in laughter as I accidentally make some "Arid Swamp of Extreme Industry" names that wouldn't likely go on a city in the middle of a forest. <shrug> It's fantasy mapping, whatcanisay?