Congratulations on your choice of smartphone. I was in your exact situation 2 years ago, meaning the N900 was my first smartphone ever, and I haven't regretted it a bit. I was so impressed in fact, that I ended up buying a few more. I just lost my first one in my vacation, and I bought an Android tab (Samsung Galaxy Tab 2 7.0) to pass the time. Android feels like a toy running on a supercomputer. The experience with an N900 is a paradox in that while the hardware is underpowered by today's standards, the phone can do almost anything, stuff that any other phone, including new models, would never dream of.

My advice:
0. Inspect it to make sure everything works including screen , keyboard, gsm modem, wifi, USB data, radio transmitter and receiver, micro sd card, camera, LED lamp, audio out and composite video out, and IR transmitter. The N900 you are getting is most likely refurbished, so checking the hardware thoroughly is a must.

1. The USB port, as already mentioned, is its glaring weakness. File the locking pins in the USB cable so that it goes in and out very smoothly. Also, approach every cable insertion like a surgical procedure, and if possible leave the phone charging at night in a locked room away from mischievous animals or clumsy humans.

2. Flash it to factory settings to start with a blank slate. Here's the detailed process I have followed successfully several times: http://talk.maemo.org/showpost.php?p...94&postcount=7

3. Read this forum and ask questions!

Welcome.