Ok, firstly, if you value your sanity, put in the extra money and go by flight!! We ignored all the tips that warned against doing the 6 hour coach ride, and I regretted it. Also, don't do it through GEM! I'd read good things about them, but this is what happened to us...
Originally we were going to be picked up from our hotel at 2.30am. Then, they phoned us and told us to get to GEM by 11pm! We did, and waited there for an hour and ten minutes, before being shipped on a tiny bus to some cafe, where we waited for at least another half an hour for a slightly bigger minibus. This shipped us to the big bus, which would carry us to Cairo. The air conditioning didn't work very well, the toilet didn't work and they only stopped once in 6 hours - at a cafe with a hole-in-the-floor toilet. In Cairo, all the "English speaking" guests were seperated and taken around in a tiny bus all day with our English speaking tour guide, who, to be fair, was great.
They start with the Museum of Egyptology, a definite must (price is included in your ticket). Then you go for lunch, where you find you have to pay for the drinks, and every toilet in Cairo has a cheeky bugger outside it asking for tips (usually just for giving you toilet roll. Always carry a pack of tissues!!!). You will then slowly be taken to the pyramids, but only after a stop at the Papyrus museum, where you will be pestered to buy things and probably told that it's the speaker's birthday! The demonstration is good though :).
You will then be taken to the Pyramids area. DO NOT let any randoms "take special pictures for you!" Before you know it you'll be on a camel, they'll have your camera and they'll be asking you for obscene amounts of money (see my tourist traps tips). Our tour guide took us up onto a hill with a view of the 3 main pyramids, where there is also an array of crappy souveneir stalls. We had to pay extra to go into a pyramid, and we were the only ones in our group who decided to go for the main one (£10!), so we were left alone and told where and when to meet our group.
Inside the pyramid is basically tiny steps going up forever, until a small room with a tomb... it's worth it to say you've been there, but for goodness sake take water with you. I nearly passed out. It's very hot in Cairo! Beware of all the scammers around the pyramids, too, some can get quite aggressive when you refuse to buy their things. There are lots of tourist police around, though, but our tour guide told us that even they are bandits!
We walked down to the Sphinx, then, which is just before KFC and Pizza Hut... yes. The whole thing is rather anticlimactic, especially if you are a fan of the once amazing civilization. To see the way that it's descendants have cashed in on their heritage is quite disenchanting.
By this point, we were reunited with our tour group, and taken to the Perfume Shop. We were meant to be given a glass blowing demonstration, but nobody could be bothered by this point, and just sat on the steps waiting until we could leave. We were then taken to a hotel to wait for the main bus. I'm sure we waited here for an hour, before being put on a bus, which was better than the one from the morning. They didn't stop at all, though, in 6 hours.
All in all... if you want to see the pyramids, do it, but fly, and prepare for a bit of disappointment. In 24 hours we were provided with one meal and expected to get the rest - and all drinks - for ourselves. If you do this trip, take water and tissues (and a big shaded hat!), don't let anyone near your camera, ignore salesmen, stick with your group and ask your hotel to prepare you a breakfast box before 8pm the night before you leave so that you have something to eat in the morning!! (and don't go with GEM... the only company I know which look professional are Tez Tours... their staff have uniforms and clipboards!)
I know what a lot of you are going to say.... a day trip does not give this city justice! TRUE! However, this was my second trip to Egypt and I missed the Pyramids due to a terrible stomach upset the first time round, so not knowing when I would return I decided to go for a day trip.... I would only recommend this to people not planning to visit Egypt again or soon as it takes 8 hours to get there and 8 hours to get back! 2 hours each way is spent collecting people from different hotels!
However it was worth it! Cairo is great! There is a buzz about this city and they have kept it reasonably green too! Then there is the Cairo museum and of course the pyramids! I would love to stay longer!!