What is the best way to control fermentation temps?

I'm a relatively new brewer, and have just been using a dark cupboard at home that stays in the 60s low 70s pretty much all the time. I've brewed only ales for this reason. The more I brew, I do find that temp has a lot to do with the end result, and want to gain more control over it. I see a lot of people posting about making slight changes of even a few degrees depending on the stage of fermentation. At this point, I have no idea how to get it from 62f to 65f... Or even referring specifically to Belgians, where I hear people talk about going into the high 70s and 80s!?!? Please.... Help me out with some wisdom on co trolling temps down to be able to adjust by a few degrees from low lager temps to high Belgian temps.

I used to throw my carboy in a large ice tub and fill it partially with water. The t-shirt covering the carboy would wick up some water so adding a fan helped bring the temps down to a level very suitable for ales (i think it was 65ish)
Now I have a chest freezer from costco with an analogue controller that also lets me brew them lagers!! I have an extra fridge as well that fits 2 carboys for lagering.
Theres alot of threads out there on carboy "cooler jackets" which let you stick ice or frozen two liters in them for fermenting lagers. I have not used one so maybe someone else can chime in?
Good luck!

low 70s ambient could result in low 80s inside the fermentor. You need to keep the temp inside below 70, i do this with a large styrofoam cooler filled with water, then i use ice packs or frozen water bottles to keep it cold. I put a thermometer in my water and keep the water between 55 and 60ish if im using a "normal" ale yeast like wyeast 1056

So far I used "son of fermentation chiller" and it was nice solution, with changing ice every/or every 2 days (depending on fermentation stage) I was able to maintain temperature very accurately.
Now, I am in middle of making fermkeezer (link below) which will serve as keezer and fermentation chamber.

if you just need heat, a brew belt and a temp controller will do the trick nicely. if you're handy at all you can grab one of those STC-1000 temp controllers from ebay or amazon and wire one up for around $30-40, which is way cheaper than buying a pre-made controller. a brew belt can be had for ~$20.

cooling, on the other hand, tends to be more expensive. converted fridges and freezers are the most popular option (you can use that same temperature controller from above), but those tend to be pricey unless you can score one cheap on craigslist or happen to have one lying around. I've seen other people build a fermentation chamber with 2 compartments - they put ice into one and hook up a fan to blow cold air into the other when the temperature gets too high. that's cheaper than converting a freezer, but you have to monitor it and keep it stocked with ice so that it doesn't get too warm. I've also seen people rip the cooling element out of an old dorm fridge and use that in their fermentation chamber, which could be a happy medium between the two (especially because most people have a mini-fridge around somewhere).

check out the DIY forum here for tons of examples of all these things.

You cant beat a chest freezer and two stage controller IMO. I have two. If you have the space...

I've been using 2 Cool-Brewing bags. Not the cheapest option but I change out 2 frozen water packs every 12 hours and keep my 5 gallon fermenters at 63 in a house that is 78 degrees. Used these almost all summer and did more summer brewing than ever before.
I'd love to have a larger chest with a temp controller on it (I do have a small dorm fridge with one) but don't have the space. These bags fold up and hide away during the winter months when I don't need them and clean easily. I've done the swamp cooler thing but it was too messy for me. This just works.