you could start with something like this. should help provide some guidance on creating a swim work out. mix it up so you don't get board. long swims and short, fast sprints should both be incorporated. like mentioned above use the interval clock or watch. many competition/practice pools might have one on deck.
google some sources to help with proper technique. you will only get so fast with poor technique. in generic terms i like to do something like
long warm up swim(s). on non-stop longer distance (500 y/m for instance) or maybe 3 x 200 (slow, speed up, medium) i would even look up some stroke technique drills you can practice here during warm up.
kick set (with kick board)
mid distance e.g. 10 x 100, 5 x 200, keep a good med-fast pace that you can hold with very little rest. 10-30 seconds. again use variety. 2 sets of 10 x 100. first set might be 10 seconds rest between at a good brisk pace that you can maintain. second set maybe go fast pace that you can maintain with more rest in between. maybe 30 seconds. the more you swim the more you will be comfortable knowing that you can hold 10 x 100 on a 1:30 interval and watch the clock etc.
recovery swim (200 or so) you can go slow, just maintain proper form. this will help move lactic acid etc through your muscles while allowing you to cool down and prepare for next set
kick set - 200 warm up kick 5 x 50 or 10 x 50 with rest intervals similar to above
recovery swim
my last set would be short distance 25 or 50 m/y. more rest as fast as you can go with proper technique. maybe 1-3 minutes between and as you get better drop the rest time a little.
long cool down swim. 200-500 yd at least.
kick kick kick. a good kick is far more important that the average person realizes when it comes to swimming. a good strong kick will propel you forward but it will also mean you will not need to use your arms to pull you out of the water since you will already be there. you will be able to use your arms to push you forward.
http://www.swimmingworldmagazine.com/swim-cgi/
http://www.swimplan.com/