I found this trick while getting frustrated with my point-and-shoot digital camera. The auto focus can't see what I'm trying to get a picture of, so I give it a little help.
Start with something tiny you want to photograph.
After deciding that the camera absolutely won't focus without intervention, gently place a finger or fingers directly behind the subject. Note the background. If it does not match the color of your fingers, try taping a matching piece of whatever is handy to a stick (or a finger ), and use that.
Half press the shutter to achieve focus lock.
This part gets tricky. Your hands are going to move. The subject likely will, too, once you release it. Try not to move the camera as you remove your finger/s from behind the subject.
Take the shot.
When you are reviewing/editing/adoring your pictures, there may be finger remnants that need cropping. This is why I like to take my photos in as high a resolution as I can.