Sure, Oase and Sharks are two of the biggest clubs with large line ups. Probably the best place to start, but there are a lot of clubs in Germany (and Austria, Netherlands, Switzerland). I've been to around 50 of them (there are many, many more), some with 100 girls easily, some with only a handful of girls. Different guys have different preferences, for me (and many others) there are better clubs than Oase and Sharks... but as you say, for "newbies" probably the most logical place to start. You might find out you like smaller or different type of clubs later on.  
   
 One of he reason these clubs are popular, is because they are easily reached from the biggest airport in Europe: Frankfurt. From the airport you can take trains or busses to Frankfurt or Darmstadt (where Sharks is located), for Oase you'll need the S bahn (nr 5) to get to Friedrichsdorf. The last bit to the actual club is best done by cab, unless you want to work with the very local public transport.  
   
 Using your credit card is a big mistake, the clubs that allow this (not in Sharks) usually demand a hefty fee. This world is all cash, but in Sharks (not in Oase) you actually have an atm (make sure to have a 4 digit pin).  
   
 1 Hotels:  
 A few hundred yards from Sharks you have Hotel Contel and there are more hotels at walking distance (like Hotel Pallas). Just use google maps or booking.com.  
   
 For Oase you need to take a short cab ride into account. Best is to take a hotel in Friedrichsdorf (for instance Mercure Friedrichsdorf) or you can see if one of the few hotels in Ober Ehrlenbach have rooms available.  
   
 2 For both clubs the best time to be there is between 5 pm and 10 pm. You still have the morning shift that started at 11am, and the evening shift will be there already as well (or will be in the proces of arriving). Girls typically start leaving from 10 pm onwards. You are allowed to stay from 11am till 5 pm btw.  
   
 3 Fridays and saturdays are the bussiest days. But sharks is pretty good at wednesday and sunday as well, because they have cheaper entry fees that brings in the locals (see website). Monday is the worst day to go to a club (Oase will probably be better), if you club on wednesday or sunday: go to sharks. Keep in mind that tuesday is dessous day in Sharks, in Oase it is thursday. Those days the girls are not nude, but dressed in underwear.  
   
 4 Difficult to say. Don't go with the first girl you see, "act like you belong there", if it's not what you imagined it is only 50 euros lost. Make sure you know which things are extra and which are not.  
   
 5 Depends on how much time you have, but in the Frankfurt area you can go to mainhattan or World, but I'd rate them below sharks and oase at the moment. For other clubs you'd have to relocate to the northwest. See if clubs like acapulco, GT or Samya are something you like. Wherever you go (with a few small exceptions) you'll find more girls in their teens than in theire thirties. A large majority of the girls is between 18-25.  
   
 enjoy