There are quite a few tutorials out there for the best practices of hummingbird and wildlife photography in general. It helps to have a fast focusing camera along with a fast focusing lens. Of course you can use manual focus and guess where the hummingbird will be but that is a side tangent. 

I haven't seen too much advice about how to get close to the hummingbirds. My number one tip to getting close to hummingbirds is use your car or truck as a blind. Setup your feeders and flowers in places so you can park a car. I don't know the science of what hummingbird's notice. I have read though they have really good memories and can even calculate when they can feed at a particular flower again. I have noticed hummingbirds are very territorial when they find a feeding territory and they watch over it. If you use your car or truck, more than likely they get used to it in their territory. I have had hummingbirds fly up to the open window and take a look inside my truck and then go on their way to feeding. This method doesn't guarantee they will not be skittish but it will give some cover.

Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower Ruby-throated Hummingbird PhotographyRuby-throated hummingbird feeding at a flower