I know that my personal method is quite chaotic, and that I'm likely missing many titles that I just have to hope I encounter later.
I read quite a number of author's blogs, and so I often know months in advance when a new book of theirs is coming out. But that's still a tiny portion of the authors I might like to read.
I listen to my friend's post about what they're reading, and what they're looking forward to, and that helps a lot especially with the new authors.
I'm sad to say I haven't found the Amazon recommendations worthwhile at all. Besides the slightly annoying tendency for half the group to be books I already own (more than a few bought through Amazon, so you'd think they should know better), it's almost rare for one of the others to be something attractive. And all too often it looks like a title is only in there because they paid to be. I don't know if that's actually what happens or not, whatever the algorithm is it sin't finding good matches for what I might buy.
So let me ask the vast readership here: what sources do you use to choose your new reading material?