Did it many years ago and although I've never been a "footie" fan - it was excellent and I would recommend it. The trophy room was fabulous.

We went as part of an organised tour so I don't really recall where it was in relation to everywhere else.

I was dragged along by OH. However, I was surprised to find that it was really interesting. We used the hop on/off bus to get there. There was a long queue but it moved fairly quickly. Avoid the shop at the end if you have children! We were going to buy our nephew a top but the prices were ridiculous. We found the official shop at the airport had much better prices.

Great experience, but also on a tour so cant help you , sorry

Once i find out what day the day trip will be on, i'll try to book online. I'm sure it only costs about twenty pounds each. Oh and i'm guessing i should be able to get a taxi on the day.

We aren't big football fans. We only want to go because it's the 3rd biggest stadium in the world.

Last time I was in Barcelona I took the HOHO bus and Nou camp is one of the drop off points. I didn't get off there so have no idea of the entrance fee, but that bus is an option instead of taking a taxi up there.

if you are travelling on your own to barcelona you can get the metro to the nou camp and can buy tickets online, rather than queue up on the day
have a look here
the hotels and local tour operators also do day trips to barcelona that includes a visit to the nou camp.
if you have any interest in football the trip is a must, but it is still a worth while visit for anyone.
as mentioned above, the shop at the end of the tour is very very expensive even for trinkets.