I have a Canon EOS Rebel T3i and enjoy it very much. The lens I use with it is an 18-55mm lens. Now I have a combo zoom/macro lens for my Canon AE1 (70-300mm) and haven't had a lot of problems shooting macro with it. However, I don't recall if I ever used flash at the time. I use that lens more for zoom than macro anyway, but have not used it a lot in recent times because I already have a load of film to be developed. So, I have not had a lot of practice with really good macro shots.
To start off, I had some problems to overcome. The first one was my flash. It is the flash that is on board the camera as I do not have a separate flash yet. My first shots ended up with a halo around the top of the photos and a darker area for the rest of the photos. Only one shot came out that I was interested in keeping. This shot is of several dimes resting in a red plastic lid from an old cake frosting container. I have no real idea how it resulted in the cool picture I got, however. Having forgotten to check the ISO and change it from previous shoots, I found afterwards that the ISO was set at 1600. I used the on board flash, and had the dimes situated directly under a bright lamp. Here is that photo. Click on the picture to see it in a larger view which will look better.
Today I determined to work out the issues I was having with the lighting. First, I worked with shutter speed and aperture settings. It did not help. I increased the lighting and stopped using the flash because every photo with the flash had the halo which you can see in the above shot. I corrected the ISO and placed it at 200, set the camera so it would not flash at all, and found out that the pictures were turning out much better, but were still not in focus. Next I worked on removing any possible camera shake by getting my tripod. That was difficult as well because I had to get the camera so close to the object (about an inch from the lens maybe?) that it was hard to position everything so that I could also see through the viewfinder. Finally, with the camera on the tripod, with the tripod tilted awkwardly, and with the lens sitting on the tabletop directly in front of the item being photographed, I got the results I was looking for. I shot coins, a knot in the wood grain of the table top, marbles, hair from a hairbrush, the hairbrush itself, text from the Bible, keys, and a very small padlock. I do believe that these first results have already shown me that extension tubes CAN be a great substitute for a macro lens if you cannot afford one at the moment. My next experiments will be in switching the tubes around and getting different focal lengths with them. More on that next time.
The photo above has details I could not seem to get without the flash. The above was using flash and you can see scratches on the table. You can see depth in the knot. But otherwise this picture is not good in my opinion. The halo from the flash is distracting, and although I could crop it out, I am not sure that the photo is worth editing. The photo below are of the same knot but without the flash.
Interestingly, the above photo was taken without the use of the tripod. It is the only photo I was able to get properly focused without it, however. The following photos all were done with a tripod. After having made these shots, I can understand the value in purchasing one of those flexible tabletop tripods for future macro photography.
If you want to find some gross things, photograph the hair from your hairbrush. Don't worry, I'm not going to post any of those bad ones. I posted this one below only for the reason that you can see this very tiny red fiber within the hair. Without the camera, I probably never would have seen it. And yes, those are gray hairs among the brown.
I've always wanted to try to make photos where people had to guess what the object was from the macro shots of various parts. While the photo below resembles stick matches, it is actually my hairbrush. I had to place the camera lens directly on top of the brush to get anything in focus. That is how close you have to get with the three extension tubes.
It is almost microscopic with the details here. In the above photo of crayons, you can see the fibers from whatever paper was last colored on with the reddish crayon. If you click and look at the photo larger, you can see the scrapings made by the paper. I was really amazed!