I sterilized bottles and nipples with boiling water. Get the water to a boiling temp first, then boil for 10 minutes. You don't need the fancy expensive sterilizer devices out there; a pot will do the same thing!
Watch the expiration dates on formula, especially the ready-made kind. If you use the ready made kind and are out and about, pay attention to the temperature. For example, in deep summer, if you keep the ready-made formula in a car, it will go bad pretty quickly. I brought powder formula with me, and used bottled water to mix as needed. However, I left it in the diaper bag once, thinking it would be okay, and 2 weeks later there was mold growing in the powder formula! This has happened more than once. It's pretty gross. If the powder is getting "clumpy" it's probably going bad. I know it's expensive, but throw it out. It's not worth the risk to your baby's health.
Oh - and like the above poster said, you can mix it up and keep it for 24 hours - but only if it's in the fridge and has never been in the baby's mouth.
Never make the baby finish a bottle. If he doesn't want all of it, that's fine. Most baby's eat too fast when they are bottle fed. When they are less than 4 months, give the bubby a burping break every 15 cc or so. This will help him slow down, and pay attention to his body when it gives him the "I'm full" cue. Otherwise, he may overeat and throw up - or overeat and get fat. :)
Start with a low flow nipple. Watch the baby as he eats. You'll know when he's ready to go up to the next flow rate.
Watch for the same cues of hunger and fullness, as you would in a breastfed baby.