Ok, so basically: wash them the most often you can. When they're very long, every day can be problematic, but once every three days is the very limit.

And if you have to take a shower without shampooing them, just tie them and stick them to the top of your head (use a hairpin or whatever), or these silly plastic tops made for that purpose. If you wet them without washing them with shampoo, they'll end greasy and sticky.

Invest in a good shampoo. Try some brands, find one which works well for you, and then stick to it. If you want really clean, strong, good looking hair, you can't really skip that and use cheap shampoo/shower gel. Really.

Brush them a lot. Ideally, each time they've been exposed to something that can make knots in them. That means, when you wash them of course, but also when you wake up, and maybe during the day also. I usually don't do it, but sometimes I really regret it. The two other are imperative.

Knots = weakness = broken hair.

Oh, and also, it's normal to lose hair. Trust me, after you brush them often, you'll lose less, but it's usually scary to look at the brush and clean it aftewards... but that doesn't mean you're going bald.