I must admit I am no expert on this. However since I have extensively used two different models in last three years, and did decent amount of online "research" before buying each of those, I can certainly give a few helpful suggestions in layman's terms. And no, I am not going to talk about digital SLR's, restricting myself to non-SLR digital cameras.
The most common question I hear,
I want to buy a good camera. Which one should I go for?
This question, to be very honest makes no sense. There is no absolute "good" camera, it all comes down to one's budget and intended usage. There are point and shoot cameras from maybe a hundred or so dollars to digital SLR's costing thousands of dollars with all accessories.
And the most common "mistake",
Choosing a camera based on mega pixels. I agree that they increase the "resolution". However, whats the point of an increased "resolution" if one never "sees" it? Again, I am no expert on this, but to the best of my knowledge, most computer screens have a resolution of hardly 1-2 mega pixels, and that's where most of the photos are viewed anyway. The small percentage of the photos do end up getting printed, and for the postcard size prints, again 3 mega pixel comes out extremely well. Unless one is printing out larger size photos at regular intervals, anything more than 5 mega pixel is virtually useless. Just to throw in some numbers, to print 10 inch by 14 inch photo in 200 dpi resolution, which apparently is professional quality, a 6 mega pixel camera is good enough.
So what does one need?
Optical zoom. That is what brings far away objects in closer focus, which is so essential in outdoor photos. However, high optical zoom almost always affects the image stability, and unless they come equipped with some sort of internal image stabilization mechanism, one should avoid them. Last seen, a few Kodak and Nikon models did not have that.
Other not so trivial factors,
Different cameras store images differently. Sony and Fuji uses extremely expensive memory cards, while most others use Secure Digital (SD) or Compact Flash (CF) type memory cards, which are getting cheaper by the day. Just to throw in some numbers again, today I saw a 1 gigabyte Sony memory card in Bestbuy for $50, while a same size SD card (which my Panasonic Lumix uses) cost me $4. When going for a long trip, the savings in memory do add up to a significant amount.
On a similar note, Panasonic uses their own battery, and consequently their own charger for it, which costs significantly more than standard rechargeable batteries you get off the shelf from Walmart.
So which one is indeed a good camera?
For beginners, or who are just interested in capturing those fun moments with their friends and family and may be occasional getaways, within a couple of hundred dollars they can get cameras with 4-6x optical zoom and 3-4 mega pixel. At this level, most good brands like Canon, Nikon, Panasonic or even Kodak have fairly "good" models.
For mostly outdoor photographers or those who have overgrown those point and shoot cameras, high optical zoom cameras are the solution. Among the 12x models, I would vote for Canon S3 1S or the Panasonic Lumix latest model. They are both very similar performance wise and do not have any major flaws. Being a Panasonic user, I'm slightly biased towards them, and should point out that Panasonic uses Leica lense, and the reaction time to save one photo and be ready for the next is incredibly small, compared to most other cameras. I am sure Cannon would have its strong points too. Last time I saw, they were available for $300-$350 range.
And for those people who wants very sleek cameras, and are ready to shell out more, I believe Sony and Casio have those.
Only those who want to have large print quality images should go for high mega pixel cameras, as I mentioned before.
And finally, when is the best time to buy?
Now. The price of most digital cameras, at least the ones I keep checking, are always decreasing, averaged over any long enough time period.