1. Clean the slide

Make sure the slide and the scanning surface are clean and dust free. Even the tiniest spec of dirt or smudge will look pretty awful when enlarged. Hold the slide by its mounting, being careful not to touch the surface with your fingers. If you need to remove dust, do so with a blower brush (available from photographic stores) or another soft brush. Don't blow on it because you're likely to spray flecks of spittle on it's surface that'll be very difficult to remove without doing damage to the slide.

If the slide is really dirty, wipe the non-emulsion side (see Dictionary) with a lint-free cloth slightly moistened with distilled water. Never use detergent. If all else fails, your local photo lab may be able to clean it for you.

Hint: You can tell the emulsion side of a slide by looking through it. If the scene is correctly oriented - not back to front - you're looking at the non-emulsion side. Alternatively, take the slide into strong light and look for ridges on the slide's surface - that's the emulsion side. Emulsion can be hard to spot so relying on the first method is usually safest.

2. Location, location

Depending on your scanner, you'll need to place the slide in a grid, or in a particular position on the scanner's surface. It's important to pay attention to these instructions because the scanner software will 'expect' to find the slide in that particular place. Never cover the calibration space (see Dictionary) on the grid (if there's one) and always let the scanner lamp warm up for the recommended time - the light colour changes as the lamp's temperature increases which can make a difference to the quality of the scan.

Make sure you place the slide right side up - the emulsion side should be facing the light source, which is usually - but not always - in the lid of a flat-bed scanner or the slide scanning attachment. If you get it wrong you can reverse the image later using image manipulation software, but you risk reducing the quality of the scan.

Most slides are mounted in plastic or cardboard, which means they sit just above the scanner's glass plate. If you can take them out of the mounting without damaging them, you may get a better result because the lens is usually focused on the top of the glass plate and anything above it will be out of focus. If the slide is inclined to curl or crimp when out of its mount try pinning the corners down with a small, flat weight like a fridge magnet. If this doesn't work put it back in the mounting.