Tip the people that give you good service in restaurants etc - they will pretty much be living off their tips. Just be wary of total strangers who hold a door for you, offer to load your bags into a cab etc, they will expect you to tip them and get a bit shirty if you don't!
Don't be embarrassed to ignore street hawkers, they know it's all a game and there are lots of other tourists around. They will see your complexion and your clothes and try to speak to you in a whole number of languages (which is pretty impressive). They know that when you hear English, or whatever your own language is, you will automatically turn towards the speaker - that's when they give you the sales pitch in your own language - don't be afraid to keep walking.
This may sound a bit strange but it is genuine advice. Don't ever show the soles of your feet in public, it's a terrible insult to the locals. Not so bad if you're, say, sunbathing amongst a lot of Europeans but not in front of the Egyptians.
Keep drinking water all day, then drink lots more. I got dehydrated once and it was horrible.
Egypt is a fantastic country, can't wait to get back to sailing on the Nile.