I stayed for a week in David's Pension in the Karlin area of Prague. The apartments are situated just 50m from the tram station and metro station. To walk to Republic square it should take 5 minutes at a stroll and Wensles square should take approx 15 mins. On a tram they take very little time.

David's apartments are quite dingy looking, we had a kitchenette with a hob and kettle, bathroom with toilet and bath / shower and bedroom with 2 single beds, TV, table chair and sink. I didn't like the fact that the sink was meant to be used to wash your hands after you have been to the toilet and to wash pots. The window is very large, but not much light is let in as there is another apartment block right opposite (High rise). The curtain is ripped and very shabby looking. The TV consists mainly of chezh channels; it also has German MTV and CNN. Just remember they are basic!

There isn't really a lot in this area, but you aren't far from anywhere if you use the tram or metro. Don't bother buying transfers from the airport to the hotel, taxis are also well known for ripping you off. I suggest buying a 24 hour travel ticket for 70 crowns, this entitles you to use busses, trains and trams. You can buy tickets from the travel desk in the airport or in the yellow ticket machines outside the airport to your right - although these do not take notes! Other tickets are available such as 90 mins, 3 days, a week etc. If you buy a 24hour ticket or more, you don't need to buy an extra ticket for your luggage. Make sure that when you get on the bus / tram or metro you need to stamp it in the ticket machine once, this will then give you the time it expires. You don't need to do it every time you get on a different form of transport, just do it the once! There are transport police that fine you if your ticket isn't stamped so be aware! I suggest using the bus 119 or 100, these will take you to the metro line, and then from there you can get the metro to the nearest station to your accommodation. There are 3 metro lines - A B and C, they come approx every 3 minutes so you don't have to wait very long. Peak times tend to be in the evening about 4 - 6.30pm. The last metro is at around 12am.

I recommend going on some of the walks on offer, if you only have a few days it helps get your bearings and usually groups are small and personal. We did the Jewish quarter tour and the cruise. The guide on the cruise tour takes you round some old town sites, then takes you to the Charles bridge for a mini cruise on the river, this is very interesting and you get a drink and biscuit whilst on board. Also do to petrin hill and look in the mini Eiffel tower for great views of the city.

Overall there are loads to do, but I think 3 days is enough in Prague.
A few tips though -
Watch for dodgy taxis and always agree a price. Lads especially watch out for friendly girls putting there arm around you, they are pick pockets who usually has a minder nearby!
There is no such thing as currency police who check your money then run off with it!
Take your own loo roll, they use really horrible stuff!
Don't have dinner or drinks in the old town square or other tourist traps as I found it isn't worth it and its extortionate!

I would recommend Prague to a friend, but not the apartments.