There are tours orientated towards The American Beaches, tours towards The British, tours that take in both WW1 & WW2, tours that take a day or 2 days....some take you to the drop zones off the beaten path, some just take you to the well known sites.

There are also the 45 seater coaches as well - but the smaller mini vans are very busy,  often quite a few parked up at the museums etc.

There are historians that are taking tour groups round, one American company does have some veterans that actually saw action taking folk round from time to time - this is very rare now as the old chaps are in their late 80's now. All the companies appear to be very professional and also very knowledgeable.

Most will pick you up from your hotel/ wherever you are staying. There are ones in Paris as well that will bring you up. But if you want the honest truth that would be a very tiring day... it's at least a 3 hour drive from Paris then to do a full day touring plus a 3 hour drive back.

 Perhaps a good solution is to do a tour with an organised company that can really give you the facts then the following day make your own way round to take in other things. The museums etc. round the area are very informative, there are English speakers everywhere.

Prices seem to vary  - some folk have been quite shocked at prices quoted.  Some of these tour companies really do know their stuff and can show you places not generally known about and can research for you if you have a relative killed in action or similar where the event actually took place - the tour can be personalised.

Find a company up in Normandy - easy on an internet search - (just type in world war tours - anything like that) find a place to stay for a few days - get a few prices and check that your guide is indeed an English speaker (that you can understand) a few tour companies do have English speaking French/Belgique but comments have been made that it has been difficult to understand because of the accent so the tour has been a little bit of disappointment. 

It is definitely worth the effort, the museums etc. are very well done with a wealth of knowledge and they are just getting bigger and better every year. The new visitor center is at Coleville Sur Mer. The American Cemetery is excellent, Utah Beach Museum is due to be extended. As well as that 2009 sees the 65th anniversary.