It all depends on how much time you have. I tried to tell a friend of mine who just went to DL about all the little surprises to look for, but since they were only at DL for a day, there just wasn't enough time.
The thing with the
Disneyland Hidden Mickey book is that it only tells you about some of the 'confirmed' ones to look for. These are the ones - many of them are very obvious - confirmed by Cast Members. However, those sly CM's have actually planted many, many HM's all over Dl, DCA, DTD and the three hotels, and most of them are unconfirmed. And they could literally be in the deepest, darkest part of a ride (my sharp-eyed friend pointed one out to me on Pirates so deeply hidden that I have never seen anyone refer to before on any HM site), hidden in a bush, in shops, out in plain sight in a very obvious location, in your food, on your bedspread, on a wall, on a trashcan, anywhere. And they don't all look the same. They are not all perfect Mickey recreations. Hidden Mickeys can just be the outline of Mickey or it could be his profile. It could also be three artfully arranged flowers in a mural, joined together to form a vague outline of Mickey's face from the front. That is the real fun of it. The Hidden Mickeys range from SO obvious to so obscure and abstract, that once you find one that is sort of atypical, you begin to think you are seeing Hidden Mickeys everywhere you go and you begin to wonder if they are real ones or if it really IS just a plant with three leaves that could sort of resemble Mickey!
So I would suggest that if you have the time, devote some of your day to scouting Hidden Mickeys. Many of them can't be seen unless you actually get on rides and things, so you might stumble upon some through the course of riding things. Just remember to keep an open mind - don't rule out any locations or possibilities. The Hidden Mickey could pop up in the most unlikely place and take a shape that is not expected! If you want to sort of spoil the surprise of finding them, check out
www.hiddenmickeysguide.com and you will see the wide variety.
Otherwise, check out the different bathroom signs, as Pink Budgie said, check out all the edible (fruit or vegetable) plants throughout Tomorrowland, check out all the pressed penny machines in DL, DTD, and the hotels, check out the 'fake gum' on the Main Street grounds which are actually magnetic sensors used to detect locations of the parade floats, get your Buzz Lightyear ride photo emailed to yourself for free when you exit the ride, etc. I mean, the thing is that, as we are discovering on this board, as many times as all of us have been to the park, there are still so many little nuances and details that we have missed. I would have never thought to even pay attention to the details on bathroom signs until Pink Budgie pointed them out, and now I am on a mission the next time I am at DL to scout out as many of those as I can! Always keep your mind, imagination and eyes open, because Disney hides little gems in almost everything they do, and many of those gems have yet to be discovered!