Before I start cleaning, I use a long algae scrubber and stir my plant leaves around a little to get anything that is sitting on it. I also have bogwood, so I move that to where it normally is. Then, I siphon the gravel. It's always best to move things that just sit in one place because stuff gets under it and, if left uncleaned, builds up pretty quickly. If you haven't cleaned under that castle or rock in a while, do it and see just how much
stuff you get up!
I siphon as much as I can without removing too much water. Usually, I've siphoned my entire 29 gallon and only 30% of the water is gone. In my 10 gallon, as much as 50% can be sucked up. I have a
Python No Spill Siphon System that connects to my sink. If you are one that doesn't have a lot of time to change the water, I highly reccomend it. It takes me less than 10 minutes with that thing to siphon and add water back into the tank. It connects to the faucet. I don't reccomend it for any tanks smaller than 10 gallons, though. The siphon tube is pretty big and sucks up a lot of water quite quickly. I just use it on my 10-gallon because my fish are hardy and can tolerate large water changes.
As far as siphoning with plants, get around the base of the plant but not directly on it. It can break the roots and the plant could die.
In a nutshell: Move decorations (rocks, wood, etc.) before siphoning. Try not to siphon where the plant roots are. Move the decorations back when you're done.
I hope that answers your question!
If you're new and haven't gotten a tank yet, I suggest a 29-gallon. Not too big, not too small. Many people suggest bigger, but I think 29-gallon is a perfect size.
Edit: Wow, there's a lot of drama on this topic! I don't think that one user is totally stupid because they've vaced up fish; I've done it a few times, but managed to free them before they've gotten a chance to get very far. It's mostly my corys; they actually swim up into the tube! They're curious little buggers.
And here is a picture of my tank to give you an idea of what I mean:
http/www.ratemyfishtank.com/enlarge.php/5593 I actually have more plants in there now. Real plants are great!!