In lots of cities I have been with the red T-shirt guides. They are nice and funny! Well, sometime you can get a guide in a bad mood, but generally it is a nice way to start getting to know a big city!!!
There are different kind of guided tours:
The free guided tour – you shall give a tip after the tour, but never more than the price they would charge for a payed one, that is what I think! Specially because there are lots of people in this tour!
Pub Crawl – where you meet people/tourists in a pub!
In each city they have some special tours like in Paris they have the Versailles Garden Tour, Montmartre District Tour, etc.
You can take the Spanish guide or the English one!
This is their blog:
And these are their websites:
Amsterdam – http://www.newamsterdamtours.com/
Paris – http://www.newparistours.com/
Berlin – http://www.newberlintours.com/
Brussels – http://www.newbrusselstours.com/
Jerusalem – http://www.newjerusalemtours.com/
Hamburg – http://www.newhamburgtours.com/
London – http://www.newlondon-tours.com/
Munich – http://www.newmunichtours.com/
Prague – http://www.newpraguetours.com/
Madrid – http://www.newmadrid-tours.com/
Tel Aviv – http://www.newtelavivtours.com/