There are lots of ways that people start races. Once you determine your upwind strategy and where you intend to start, you then must figure out how to start in that location. There are several main starting techniques: timed run, port-tack approach, stop & go, and a dip start.
Starting Techniques and Good Starting Practices
The Timed Run start may be the easiest way for novices to start. You sail past the location that you want to start at on a reach on port tack, and look at your watch. You divide the amount of time to the start in half, and sail along your port tack reach until that half-way point. You tack around onto starboard, and head back towards the line on a reach towards your intended starting place. If your speeds are equal, you should get to the line right a second or two after the start. To increase the accuracy of your timed run, don't use it for long periods of time - I wouldn't sail longer than 30 seconds from my intended starting place. If you start your timed run with four minutes to the start, you risk getting too far from the line. What would happen if the wind died when you tacked around and tried to head back towards the line? You'd be really late for the start.
The Port-Tack Approach is can be a good starting technique, but isn't for the novice or faint-of-heart. Essentially, when all the boats are lined up on the line on starboard tack and waiting for the start, you cruise below them on a port tack reach. When you see a nice spot to start in, you tack onto starboard into the hole. The drawback to this starting method is that you may not find a hole where you would like to start, and will have to duck the whole fleet before you find a spot to tack onto starboard for the start. However, there are times that you can port-tack the fleet at the start, and cross ahead of everyone on starboard. The Port-Tack Approach also works well if you're behind in your starting plan, and are looking for a last-minute solution to a decent start.
The Stop & Go start method is a favorite of college sailors around the country. The technique is simple: you park yourself a boatlength or two below the line at the position that you want to start at on a reach with your sails luffing. When you get close to the start (say 15 seconds or so), you pull your sails in and accelerate towards the line. You'll have to practice this technique a lot, because it takes time to learn how to accelerate your boat quickly (and legally), and it also takes practice to determine how much time you need to accelerate your boat to full speed. Generally, this technique requires carving out a "hole" to leeward of you. That way, you can pull your sails in, bear off a bit to accelerate to full speed, and then crank your sails in and head up so that you're one the line and moving fast at the start.
Another great starting technique is the dip start. It's great for starting in the middle of the line when there's a lot of midline sag or if there's a lot of current coming from the windward mark, pushing boats away from the line. You need to know exactly where the line is to pull this start off, and you also have to know if the race committee is flying any flags (such as the black or I flags) that would prevent you from legally starting in this method. With these warnings mentioned, we can get on to the technique. It's very easy: you reach along starboard tack above the line towards the place that you'd like to start at (you need to do a bit of a timed run so that you're in that location at the start). As the clock ticks down, you bear off and duck below the line, then round up at the start. Essentially, you dip below the line for the start.
Here are a few good ideas for helping you achieve good starts. One essential thing to do is always know what the race committee is up to. Many people hang out and talk to friends while waiting for a race to start, but when the starting sequence begins, they don't know what's going on. Which course is being sailed? Which division is starting? Is there a black flag or I flag up? Was that a general recall or an individual recall? Make sure that you memorize your sailing instructions before racing - some sailors even tape laminated sailing instructions or zip-lock bags with the sailing instructions to their hull so that they can always know exactly what the race committee is doing.
Another idea is to never get too far away from the line or the committee. I've seen people go for a lazy Sunday cruise hundreds and hundreds of yards from the line in light air. When the committee begins a starting sequence, those folks who sailed so far away are unable to make it back to the line in time for the start.
Finally, it makes sense to know what the current is doing. Is it trying to push you over the line early? You better leave some extra distance between you and the line so that you aren't OCS (On Course Side) at the start. Is it pushing you away from the line? Perhaps you might consider waiting for the start sequence above the line and starting using a dip start to assure that you'll be at the start on time, and not crossing the line a minute late.