Claire;
I will not call this top tips exactly, but it might be a start.
A good site for tidal info in Norway is
http://www.math.uio.no/tidepred/
Choose location ("Vel stasjon"). Go for Røst.
First day ("Dag for start")
Period for prediction in hours ("Varsling for perioden, timar")
In beginning of August, there will be around 1,2 m difference between low and high tide. I have not (yet) been able to find local info on current directions etc. But be aware that even if the tidal differences are not impressive, there may still be strong currents due to large fjords emptying and filling. Particularly in the areas Vestvågøy, Flakstadøy, Moskenesøy, Mosken and Værøy there will be strong tidal currents like Nappstraumen, Sundstraumen and also the more widely known Moskenestraumen (ref. Edgar Alan Poe's description from 1841: "... sending forth to the winds an appalling voice, half shriek, half roar, such as not even the mighty cataract of Niagara ever lifts up in its agony to Heaven." Have a nice trip!).
As for favourite spots, I have never paddled in Lofoten myself. But even if I have made frequent visits to the area in the past, I frankly do not know how to advice you. In short; you can hardly go wrong. If you mostly or exclusively will be wild camping you have unlimited options, if you will be staying in rented cottages you need to plan your route accordingly.
If you want to test ideas, use the excellent resource
http://norgeibilder.no to zoom in to the areas in question and take a look at the aerial photos - a lot better resolution than Google Earth. You'll soon spot the many sandy beaches between the rocky mountains.
Bringing a car or not? Depends entirely on your plans. You could leave it at Bodø and take the kayaks on the ferry or Hurtigruta across Vestfjorden to Svolvær (or the ferry out to Røst if you prefer), but this will limit your range. If you go to Røst you will not need a car though.
Have you tried the local tourist information, BTW?
http://www.lofoten-startside.no/engelskindex.htm
Apart from that, well, Lofoten is of course Lofoten. But personally I prefer Helgeland a bit further south (between Trondheim and Bodø) for kayaking.
Regards,
Erling.
Growing up is for trees.