Hi, and welcome! There are lots of different ways to label books, and even the most scantily-labeled books do sometimes get journaled while the heavily-labeled/stickered/stamped ones might not, so you never know. My preference:
I put a label-with-BCID on the inside front cover. (I generally reserve my custom bookplate labels for hardcovers, and use the free-download labels on softcovers, but there are exceptions.) That's the bare minimum, btw; either a printed label or a hand-written one with the BookCrossing URL and the BCID, plus some minimal "why you should look at this" text. All the rest of my suggested labeling is optional, though I do think it may help improve the odds of getting journal entries on books down the line.
I have a couple of custom stamps with the BookCrossing URL and some basic info ("Where's this book been?" or "Read. Enjoy. Release." or "Visit this book's online journal"), and I use those to stamp the title page and the last page, writing the BCIDs in under each stamp. (I figure that's insurance against the loss of the main label, and the entry at the end of the book might help remind the reader to journal the book if they opted not to do so when they first found it.)
I like to use stickers on the book's spine or outer front cover; there are several different styles available in the Supply Store, from the tiny stickers that fit on most book-spines and have Ballycumber and the BookCrossing URL to the larger, more colorful stickers that might be more likely to draw the eye. There are also free-downloadable sticker styles in the "user-created labels" thread in the Activists forum ( http://www.bookcrossing.com/---/358601
), though some of the links posted there may no longer be active. You could even design your own, if you wanted; adhesive return-address labels are a good size for this kind of sticker.
That's what I do for all of my books, whether I'm planning to swap them directly with other BCers or drop them off in OBCZs or Little Free Libraries or other book-swap shelves. If I'm going to leave the books out in some public place, though - what I consider "truly wild" releasing - such as on a park bench, a window ledge, a public sculpture, hanging from a tree, etc. - then I'll usually add a sticky-note to the front cover to announce that the book is free to whoever wants it. (There are supply-store versions of these, which I like to use, but I also resort to Post-it-notes in eye-catching colors and shapes, on which I hand-write "Take me! I'm yours!")
For more on different labeling and releasing styles, check out the Release Techniques forum. This thread ( http://www.bookcrossing.com/---/518626
) has some comments on labeling styles, and you might find some of the other threads of interest too.
All that said, don't fret about it too much. It does help that the book is obviously free to the finder and not lost, and of course the BC information needs to be present and legible, but beyond that it's really up to the finder and their level of interest in the book and in the "traveling" concept. I do recommend checking out the Site Watch forum for examples of books that have checked in, sometimes long, long after they were released; it can be entertaining and, if you haven't had a catch yet yourself, comforting, to know that people are indeed enjoying the books!