-----------------------------------------------------------------------------------------------First off find one of those CD player cleaner dics and run that in the dreamcast...no dont play the first track over and over to clean it or whatever just open the dreamcast lid put the disc in close the lid let the disc get detected and repeat so the bristels hit the lense repeadedly.
Then get a Q-Tip....those ear cleaner thingies....and run that over the lense lightly and then roughly...not TOO roughly...your doing it too rough when the lense goes all the way down into the dreamcast
now take a paper towel...more than one actually, and some windex (or some other glass cleaner) and put windex on the paper towels and clean every possible nook and cranny of the dreamcast with the paper towel, where the disc goes AND the outside...now take some dry paper towels and dry it off...your Dreamcast should now look shiny new
make sure to take out the modem and clean in there too!! although it doesnt usually get dirty in there but it cant hurt it to be clean hehe
no for the controllers (yep you can clean the controllers while you wait for the Dreamcast to dry entrely)
do the same thing with the windex and paper towels and make sure to get all parts of the joystick and buttons you can movie the joystick in all directtions to reveal more of the ball-shaped part the stick is on
now get some tookpicks to clean out the letters in the buttons and the cracks on the side of the controllers where the top and bottom half of the plastic meet and you should be able to get any dirt out of the controller this way.
now get some windex and cotton balls and clean the inside of the controller plugs using the cotton ball and clean teh outside too...you will be surprised how much crap comes out of these hehe if you want you can do this on the plugs on teh Dreamcast where you plug these in but these usually stay pretty clean
Now for the VMUs/Other controller accesories
get more windex and paper towels (god i love windex
for teh contacts i take more Q-Tips and pick some of the cottoney stuff off to make the ends smaller to they will fit and then i spray windex on then and then dry it with another Q-Tip
do the same with Rumble Packs/etc. except theres no screen but use your windex and paper towels damnit!!! lol
Now for lightguns!
go over it with your paper towels and windex again (this sounds like a big windex ad buy now i know but its very useful!!!) and then use the same for teh glass lense at the end!! and then get the toothpicks out again and clean all the nooks and crannys like you did with teh controllers and use the same method you used for the controller plugs to clean the light gun plugs
use the same methods to clean all your cables and such too that i mentioned above...those usually dont get too dirty but they can hehe
VGA boxes
pretty much just go over it with more windex and towels....you should be pretty good at it by now hehe so i wont go into detail
now DO NOT play your dreamcast for a couple hours (its really hard to survive without it i know