Beginning the winemaking process:
Crushing the grapes
Once picked, the grapes need to be processed according to their winegrape type. White grapes like Chardonnay, Sauvignon blanc or Viognier require processing while cool to preserve their fresh fruitiness. In fact, keeping all white juices and fermenting wines cool (if not cold) is the name of the white wine game. White grapes are not normally fermented with their skins (may benefit some varieties but is unusual) - the juice is pressed from the crushed (or not, if you have a whole cluster press!) and cooled quickly. Please be prepared to ferment this juice in a cooled location as white wines retain the best of their delicate flavors and aromas with cool fermentations. Unfortunately, I cannot help you with pressing white grapes!
Red grapes, like Cabernet, Merlot, Malbec, Petite verdot and Zinfandel are crushed and fermented with their skins so that the flavor and aroma compounds are captured from their skins. They are normally fermented with (or "on") their skins at warmer temperatures so that these compounds are quickly expressed.
Interestingly, there are two interesting processes that you might use in your red wine processing.
COLD SOAK is a method of keeping the must cold (by refrigeration or use of dry ice) for 24-48 hours to allow for the early extraction of important compounds from the skins. These is some controversy regarding how well this works. Even in the industry, there are some who swear by it and some who swear at it. It may be valuable for some varieties and less valuable for others. DOES IT HURT? Only if you can't keep the must cold enough. Even with the SO2 addition you may encourage mold growth with this technique if you go beyond 48 hours. So use care.
EXTENDED SKIN CONTACT (beyond the end of the yeast fermentation when the must is "dry" or the sugar is completely fermented) is used to wring out all the flavoring compounds in the skins as well as encourage the formation of long chain tannins to fast forward that aspect of ageing. DOES IT WORK? Again, it probably depends on the variety. You have to be vigilant and restrict oxygen access or run the risk of encouraging VA. Wineries have an easier time as they can just close their tanks enough to allow the entrained CO2 to slowly come out of the wine and provide protection in a semi-closed scenario - they can also gas a tank to prevent oxygen contact.
TEMPERATURE OF FERMENTATION: The most basic rule is don't let your fermentation cap temperature (the skins in red fermentations that rise to the top and then need to be punched down!) get over 95 F. This is the point that yeast die and, although, you might not see this happen immediately, as the wine temperature under the cap will be less than 95, you risk killing enough yeast to make the hard end-of-fermentation fermentation slow or stop. YET, you must keep the temperature warm enough to allow for good extraction, which happens over 85 F! A garage will not be consistently warm enough UNLESS you do something to keep the temperature consistently warmer (think germination tray electric pad warming units). This is NOT true for white fermentations which you need to keep as cool as possible, either through refrigeration of the juice or constant, judicious helpings of dry ice.
PUNCHING DOWN: Just about anything works but think sanitary and use something that can be washed and sanitized. Beverage People has a great stainless steel punchdown device that works well but other suppliers probably have devised something too!