I plug my camera's CF card into a SanDisk card reader on a USB port. The card shows up as a volume in the Finder, and then I drag my photos to a folder on my hard drive. (Rather than using Image Capture or any other program.) I check the files using Quick Look to make sure they got onto the disk, before I delete them from the CF card.
I have scanned old pictures, both slides and flats, using an Epson 4490 scanner, and had good results. It takes time though, between 5 and 10 minutes per picture.
I sent hundreds of slides to
ScanCafe.com, who scanned them to disc in India at a low price. This was very satisfactory.
I try to remember to make the original files read-only just after I copy them to the Mac. The idea is that my original should never be changed.. always work on a copy, so if I screw up or change my mind, I can recover.
Never have only one copy of a file you care about: back it up. I have a folder which contains all the originals, in subfolders named things like Nikon8, Nikon9, etc. When a folder gets near to 650MB, I burn it to CD-R and start a new one.
I wrote up a
useful cookbook about how I prepare photos for web use.
I look at newly loaded pictures with Quick Look, and if they should go on my web pages, I open them in Photoshop. I straighten and crop, and adjust curves, and then run a standard saved action that changes the image size and runs Smart Sharpen. Then I save the result as a JPG using Save for Web. Usually a quality of 30 to 50 looks just fine. The input picture is usually around 3MB; after processing, I end up with a file around 50KB. I drop the converted pictures in a folder and edit a file that has a caption for each file. Then I invoke software I wrote to generate thumbnails and run a Perl program to regenerate the album web page. (Thumbnails are generated using the "convert" command from the ImageMagick package.) Each album page shows the thumbnails and can pop up a view or slide show of the converted pictures.
I copy pictures into iPhoto for displaying on the Mac. The Mac's screensaver will display an iPhoto album, and that's how I set up our living room computer to show snapshots at random.

On the living room computer, I have several thousand pictures in iPhoto. For each picture I add, I edit and straighten and crop it if necessary. Since the display is an HD TV, I try cropping to 16:9 if the picture can stand that: doing so will eliminate black space at the sides or top of the picture. Then I try the "enhance" button to see if this makes the picture look better. If not, I may try individual functions from "Adjust" but I don't spend a long time on it. Some pictures are improved on our TV by using the "Definition" and "Saturation" sliders. I have an iPhoto album called "screen" and add pictures to it if they should be in the random screensaver.
Recently a friend said they found iPhoto's distinction between Events, Albums, and Tags confusing. I think it's over-complicated too. The basic idea is that each photo is in exactly one Event, but it can be in any number of Albums (including none), and can have any number of Tags (including none).
There are programs like Picasa, Adobe Bridge, etc that help you manage your collection. I have tried a few of them but don't use them consistently.
Another thing I have not gotten into is shooting in RAW format. This makes bigger disk files but would mean I could adjust a lot of things like white balance later. The real expert guys who spend a lot of time making their pictures perfect shoot RAW. It is especially important for photos that will be printed on paper.