If you use any sort of heat styling on your hair (or you simply have dry, delicate strands) it is imperative that you use a deep conditioner once a week. Ever since I've started using one, I've noticed that the number os split ends I get has been reduced to nearly zero, and my hair just feels softer and healthier overall.
My favorite deep conditioner is Neutrogena's Triple Moisture Deep Recovery Hair Mask ($6 at drugstores). It's inexpensive, feels nice and rich going on, makes my hair feel unbelieveable soft and silky after rinsing it out, and just makes my hair feel so much nicer in general. I've briefly tried other deep conditioners to see what else is out there, but this one is by far my fave. Yet another success by Neutrogena.
I normally would have a really hard time trying to keep track of when I did x, y, or z for the week so I was initially unsure of how well I'd remember to use this conditioner once each week. What I've found really works is to use it on sunday night (or whenever night I wash my hair that's closest to the weekend/beginning of new week border). The switch from one week to the next is enough of an "event" at the end of each weekend that I can attach this little extra shower routine to it and can remember to do it a bit more easily. This is what works for me, y'all can certainly figure out what works best for you and your beauty routine. =)