Using the term "ASA" is a dead giveaway that you were probably brought up using a manual or mostly manual camera.
1. Set ASA/ISO - you'll find that today's digital cameras produce extremely high results at ISO up to 1600 - well beyond anything film could ever do! 2. Set either aperture(f/stop) or shutter speed depending upon desired result - depth of field, stop action, etc. 3. I suspect most people use the in-camera light meter to make adjustments. You can also go absolutely manual by using the BDE (Basic Daylight Exposure) principle - shutter speed at f/16 = inverse of ISO (if ISO is 100, then correct exposure is f/16 at 1/100th) This of course supposes direct sunlught with sun behind you. Then, you can adust for sidelighting, backighting, hazy, cloudy, etc. 4. I utilize a combo of BDE and in-camera meter and often use my old hand held analog meter. 5. Post exposure I use a Hoodman loupe to check image via lcd and set my playback to show any blownout areas of image. I don't use histogram at all. I find the loupe really assists in checking the image in bright light