I've recently been getting into the hobby of Geocaching. However, I'm finding there are many, particularly in cities, that I just cannot find no matter how hard I look for them. They tend to be very small, and often have camouflage of some kind. What tips can you offer to help me improve my rate of finding them?
Read the cache page closely. There may be hints in other places as well as the obvious encrypted hint - the cache description, title, and previous logs may all pose clues that would help you on your search. I tend to try without first but if I'm really stuck I'll read all I can to try and give me a bit more of an idea.
Bear in mind that the co-ordinates are often only rough. I've found a couple of caches where the co-ordinates have been 60m off! Bear in mind that you'll have the inaccuracy of the original person who grabbed the co-ordinates as well as the same of your own GPS, so in places with poor coverage it could be wildly out. If the place your GPS guides you to doesn't make sense, don't necessarily stick to that one spot, walk around, but...
Don't scout randomly, use a methodical route. All too often people make the mistakes of walking around randomly and coming back to the same couple of places, missing the more subtle place that they would have found otherwise... I tend to check the obvious places first and then cover the area more thoroughly.
Look up. People often look down and all around them for clues, but I've seen people really struggle to find caches in plain sight if they're above head height! Equally, look up for clues as well - I hid a cache with the clue "underneath 3 cables" (those cables being cables in plain sight running about 20 foot in the air) and you'd be surprised how many people looked for ages because they didn't get the clue!
Bounce ideas off someone else. If you don't understand the clue, ask someone else if they have any ideas. Sometimes something you've been pondering over for hours can jump out near instantly to someone else! One particular clue was "CND", and the cache site was a few fence posts roughly in the shape of the corresponding flag. Being too young, I had no idea what "CND" meant at all - my parents were right on it however!
Remember that caches can be all sorts of objects. They're not always just the obvious tin - I easily found one recently that was a (toy) frog, and many people had missed it on the assumption that just couldn't be it.
Know when to give up. Seriously, if you can't find it having searched around for a couple of hours and the previous 6 logs were all DNFs (did not find), there's a very good chance it's no longer there. Leave a note and ask the cache owner to have a look if they aren't already.
Remember to mark a waypoint for your car. Not strictly to do with finding them, but especially if it's a cache that involves wandering around and you're not exactly sure where you are, mark a waypoint for where you started / parked / know where you are. Takes all of 2 seconds and could save you wandering around lost for hours.
Overall though the best way to find them is practice - the more you end up finding the better you'll get at it and the more spots you'll notice that you wouldn't have otherwise. When I first started I was spending a long time finding most of them, now it's usually pretty quick!
Look for patterns: if several caches have been placed by one owner, what kinds of containers are being used; are similar hiding places being used.
Logs: look at photos - the person may be blocking the actual hiding place, but the background may be a clue; if the cache container is shown, you know its size, shape, and color. Also, log may state, "have seen this type of cache/hide used recently".
A flashlight has helped, even in daytime, to see a shape (such as a smooth, round top) or a color that doesn't fit with natural surroundings.
I've only been geocaching since June 2010 but only in the last few months did I finally figure out what to look for and my count has soared. Now I'm in the process of placing my first hide. It takes practice. At first, all I did was tag along behind veteran cacher pinkdolphin, my mentor and friend in NC, who has logged almost 10K finds. I could never figure out how she could just walk right up to it, while I remained poking around stupid leaf piles :P It was very frustrating. However, I followed a few pointers which I now pass on:
Remember to have fun, enjoy the chase and being out of doors, and good luck to you!
Purple Abacus in MN
In cities, an issue with geocaching is the accuracy of the GPS - you need to assume a greater margin for error than when you are in the open countryside as tall buildings do affect the signal.
As @xpda says, some sort of regular search pattern may be required, and be aware that geocaches may be hidden out of reach of average passers-by to avoid them being discovered accidentally, so don't just look between ground and eye-level. Also look above you, and at the ground - are there loose stones, gratings etc?
First, pick the location you think it closest to the mark, based on the GPS. Then, walk in an outward spiral, looking at any place that someone would be likely to hide a geocache. Think like a person who is hiding it. Where would you put it? Don't forget to look up. Maybe it's at eye level or above.
If you wander around randomly, you'll end up walking over the same places over and over. If you force yourself into a pattern, you'll see things you would not otherwise.