Most of these may seem really simple, but I'm just going to go ahead and list them because I'm on Adderall and feeling down for some typing. Someone might get something out of it.
1. Alcohol and d-amp are both diuretics, flushing a lot of water and water-soluble vitamins, so keep hydrated and get your vitamins.
2. Both fuck with sleep. If you use much alcohol to pass out from amps, you're going to have much poorer sleep quality than without alcohol. A little melatonin, a hot shower, and forcing a meal down your gullet aren't as good at making you fall asleep, but those and simply taking your amps earlier in the day will be a lot healthier.
3. Find a usage pattern that gives you the most fun with the least drug administered. For me, I get the most euphoria out of amphetamine by dosing early and not trying to get that state back after I start to come down. With alcohol, I find the act of drinking itself very relaxing, so I sip at 3-6 beers over a few hours.
4. The route of administration and formulation of the drug matters a lot if used frequently. Sublingual and oral are some of the least damaging ways (compared to sniffing pills or IV) of getting amp into you. A beer is probably going to be easier on your gut and teeth than chasing some whiskey (relatively high conc. of a solvent) with some Coca Cola (sugar and acidity).
5. Watch your polydrug use. A lot of people love to chain smoke on stims or alcohol.
6. Exercise. A natural relaxer, helps a lot with the anxiety or depression than can lead to greater drug use. Amps can lead to atrophy if you're exhausting yourself with poor nutrition often enough. With amp use, exercise should also go with a diet that gives you a net excess of calories per day.
EDIT: Oh, and, if it counts:
7. Social health. Make sure you don't need amps or alcohol to be able to socialize. Also, when you're sober, take a step back and look at how you act on stims or alcohol. Do you look like some twitchy sketchball? Do you show visible signs of being tipsy at school or work?