Have you read a good homebrewing book? If you are just relying on the instructions from the kits you are really short changing yourself. Pick up a copy of John Palmer's How to Brew
and read it. You will learn what different malts do, how to change flavors in your beer by different techniques, things you are doing wrong you would have never gathered from reading the kit directions.
Another good book, altho outdated compared to Palmer's Book, is Charlie Papazian's "The Complete Joy of Homebrewing".
Try a few recipes out of that book and I guarantee you won't find two that taste the same.
In addition to all this, seek out some different kits. Check out the kits at www.northernbrewer.com
. Those are solid recipes and they make great beers. Most of the "dump a can of malt extract" kits with the yeast taped under the lid make crappy beer.
In addition to this:
Use oxiclean to clean your equipment. Then use StarSan or other no rinse sanitizer to sanitizer. (See the links above for those sanitizers)
Be sure to use a quality yeast!! If you are simply using the yeast that comes with the can of extract you are really limiting yourself. For a beginning brewer I highly recommend Safale US-05 Ale yeast. Its a dry yeast, you don't need a starter, it's clean fermenting and aeration is not as critical. Liquid yeast is great and you will have a vast library of different yeasts to choose from once you get the handle on fermentation - but US-05 makes a great, clean beer. I have been brewing for 15+ years and this is my go-to yeast when I want clean fermentations. It simply can't be easier to use!
Be sure to use FRESH ingredients. Old cans of malt extract don;t make very good beers.
Be sure to control fermentation temp, including pitching temp. Always cool your wort down to below 68 degrees before aerating and pitching your yeast and keep fermentation temp - which can be 4-6 degrees OVER ambient temp - under 68-78 degrees for most ales. If you are fermenting at 72 degrees room temp you are fermenting way, way too warm and this can be a cause of off flavors that will taste the same every time.
Finally, brewing is a craft and it has to be approached that way. Too many people approach it as like making a box of Macaroni and Cheese. You really have to sit down and get a handle on what you are doing before you are going to make truly great beer. This does take time, but the books I mentioned above will get you pointe in the right direction. Good luck!