Let's see... I got my first SLR in 1999, had a point and shoot Canon for a couple of years before that. Recently got a full frame DSLR. The vast majority of my photography is done when hiking, so light-ish zooms are a big boon for me.
17-40 (landscapes, or for visiting old cities like York with really tight narrow streets)
24-105 (general purpose walkaround lens - my most used lens)
100-400 (compact for great reach - if I'm in an area that I know has interesting wildlife, this will be on the camera body)
The above 3, and camera body, fit into my Lowepro Street and Field Rover AW backpack leaving me space for food, drink, waterproofs and some accessories (filters, etc).
I also have a ef100 macro, that is really sharp and also gets used a lot for portraits.
Tips? Take photos and enjoy life!