7D is not a beginner oriented camera... it seems to be designed with fairly experienced shooters in mind. It takes some time and effort to learn to use it... and then it can perform quite well.
My best suggestion to get you up and shooting quickly is to keep it really simple...
Use One Shot and AI Servo normally.... One Shot for stationary subjects and AI Servo for moving subjects.
I suggest mostly to use Single Point AF and select the point manually... probably the center point most of the time (though don't hesitate to use any of the others, all 19 are the better dual-axis/cross-type). This leaves you in control of the AF, not leaving it up to the camera to decide where to focus (Expansion Points, Zone Focus, Auto/All Points all leave a lot to the camera, but they have their uses in some specialized situations).
Yes, the first thing to do is go into the Custom Function, to Autofocus/Drive, C.Fn III - 6... and enable all the options there (two or three will already be enabled).
Next go to C.Fn III - 1 and set AI Servo tracking sensitivity one notch toward "slow". This determines how fast the AF jumps from one subject to another... it doesn't slow down AF. With practice using the camera, you might be able to turn it back up. Also, if shooting a subject that changes direction a lot, with few or no obstructions, you might be able to turn it up a notch toward "fast".
I suggest using Single Point, manually selected, most of the time. Probably the center point mostly... but the others are usable and you can navigate to them normally.
Spot Focus might be useful, too. It uses a smaller AF point, for greater precision. It's also a single point, but Canon doesn't recommend using it all the time because it's a bit slower tracking movement. I mostly use it for stationary subjects and One Shot. But, some people use it successfully with AI Servo and moving subjects... It probably depends upon your lens, as well as the ambient condition... light levels, subject contrast and detail.
The times I find Expansion Points and Zone Focus most useful is when there is a single subject against a plain background... for example a bird in flight against a blue or solid overcast sky, or a few distant clouds. If using a long lens relatively close, be sure to set an f-stop that will cover wingtip to wingtip, have plenty of depth of field, so that if the camera chooses to focus on the closest wingtip you won't have the rest of the bird OOF.
Back Button Focus
really helps with action photography and makes it possible to leave the camera in AI Servo all the time (you can use it just like One Shot, except lift pressure off the rear button when focus is achieved if you want to use a focus/recompose method for example). 7D is highly configurable, to set up BBF, for example, you can go into the Custom Function menu, Operation Others, C.Fn IV-1.... change the shutter release button to "metering only" in the half=press position, leave AF-On button at it's default setting. Or you can switch AF-On button function with the */AE Lock button function, if you wish.
Two other things often mistaken for focusing problems....
7D uses a very densely packed sensor... which might make it more susceptible to camera shake, a little more likely to blur an image due to movement. In a white paper Canon recommended using a little higher shutter speeds whenever possible... Using mirror lockup and other stabilizing methods when it's not possible. I just use a stop higher ISO than I was in the habit of using with previous cameras.
Also, 7D uses a strong anti-alias filter, to prevent moire with such a densely packed sensor (it has twice as many pixel sites per square mm as 5DII/III, for example).... So 7D images tend to need more sharpening than images from many earlier cameras. If you shoot JPEGs, dial up in-camera sharpening. If you shoot RAW, dial up sharpening in post-production (unless using Canon DPP and letting the software use the in-camera settings to process images).
Keep it simple, it will take a while to learn a lot of the 7D's modes.
You have to learn to trust the camera... It's very fast focusing and the two I've been using for a couple years now very seldom let me down (still miss a few... but it's hard to say if it's me or the camera in a lot of cases).
Oh, and in One Shot you won't see the AF point blink red Focus Confirmation when focus is achieved (the green LED will light, and if you have it enabled you'll get the audible "beep").... This is because of the transmissive LCD used for focus screen. You can use Autofocus/Drive C.Fn III - 8 VF display illumination set to 1:Enable to turn on a red flash overall, if you want it. (Default is "auto" which will only work under certain conditions).
On 7D and all Canon for that matter, there is no Focus Confirmation in AI Servo (can't be, it's continuously focusing) so this doesn't matter. But a lot of people coming from other cameras are accustomed to seeing the selected AF point(s) blink red momentarily to indication AF start when in AI Servo mode. You won't see that in 7D. The selected AF point(s) are the only ones displayed on the 7D's focus screen. On other cameras, all AF points are displayed all the time. On 7D, only the active one(s), are shown as black boxes. Once accustomed to it, you can tell immediately what mode and selection you have set... just don't expect it to blink at you.
One tool I find very handy is the "on demand" grid in the viewfinder... it really helps me keep my horizons level and vertical objects vertical! To enable the grid in the viewfinder, you need to go into the menu, the second Yellow Wrench tab, it's at the bottom of the list. (There is another grid display choice in the fourth Red Camera menu tab, but that's the one for Live View on the rear LCD monitor).
Finally, coming from a 10MP camera you might be in the habit of viewing your image files at 100% on your computer monitor. If you do the same with 7D, the much larger 18MP images will actually be displayed far larger and you'll be looking at them much more critically. So they might actually appear "worse". Don't expect them to be "better" unless you scale things the same way: Either back off to about 50% when viewing the 7D files, or resize them to the same dimensions of the images from the 10MP camera, if you want to compare.
