It is better to scan at a lower resolution than to scan at a higher resolution only having to resample the image size down. If you intend on printing your images, you should not have to scan at a resolution higher than 600 dpi. Also, scanning is a system-intensive process. It's a good idea to close other applications while scanning. If you are purchasing a scanner and would like to scan magazine or newspaper content, you will need the ability to descreen these images.
Halftones are pictures constructed with dot patterns.
When a halftone image is scanned, it will produce a distracting pattern of lines called Moire. There are a couple of ways to prevent this. The best way to reduce this pattern is by using the descreen option that comes with some scanners. This will keep the proportions of the image constant. Try rotating the picture 30 degrees or so and rescanning.