What exposure setting do you use? Most SLRs offer a choice of at least three – matrix, centre weighting, and spot. Often the matrix setting will give satisfactory results, though if the background is brighter than the subject it can leave the subject over-exposed unless you use fill flash, but fill flash is a different topic. With a bright background I prefer to use centre weighting or spot, and now we have the problem that both of those evaluate on the centre of the scene, and often our subject is not at the centre of the scene.
But just as last week we saw that we can lock the focus on the subject, then reframe before taking the shot, we can also lock the exposure. One way is to point the camera at area that we want optimally exposed and press the exposure lock button. The exposure settings will then remain unchanged until the next time the shutter is released. I generally use this when taking a bird on a branch. The bird will be relatively small in the frame, and seen against the sky, so even with spot exposure it is likely to be under-exposed, so I point at the trunk of the tree, lock the exposure, and reframe to take the bird. Of course, most times the bird will have flown by then, but sometimes you get lucky.
The other way is more useful if your subject is relatively large – a person, for example – and off-centre, as they probably should be. Since you will be using focus lock on the subject, you set your camera to lock the exposure automatically when it locks the focus, so that both are locked on the subject before reframing to take the shot. You may need to use the custom settings in your camera’s menus to tie the aperture lock and focus lock together, but you will be pleased with the results.