Worms/Heartworm, flea questions

Hi, thank's for all of your help and wonderful website.

I have a question about worms,heartworms and fleas.

First of all, I always had big dogs and never worried much about their health as they were very healthy and lived to ripe old ages without many trips to the vet. Plus all of the things that are available to the dog owner now that wasn't around back then, i'm not sure where to turn.

Now I have this little guy and and he is a treasure, I am worried about worms, heart worms, fleas and all those things I really never had to deal with before.

I have checked his bm and it doesn't look like he has worms, but my husband noticed him rubbing his bottom on the floor the other day and I don't know if that's an old wives tail that there is a sign of worms or not. Can you see worms in the bm after it is dried?

What causes worms, and heartworms and should I just get him meds even though he might not have them?

I've noticed a lot of biting after a Christmas day outting where he was a perfect gentleman and didn't once lift his leg and happily played and showed off for everyone. These people have 3 dogs and a cat, I am sure my little boy has fleas now. Back in the olden days, you bought a powder or a spray and applied it and hoped it worked. Now there are 100 different products on the market and frankly I can't afford to buy a bunch of products that don't work.

I've been waiting until after the holidays to take him to the groomer, she will check his anal glands and drain if necessary, flea shampoo and clip his nails if need be. He has already had flea bath using a over the counter brand of shampoo in the kitchen sink. I'm trying to find a good vet (asking everyone I know where they go)then he will be neutered.

I hate to brag, but the first day I brought the crate home, he of course went in and checked it out. Later that day I then put him in it and gave him a treat and left him for about 20 minutes. Other than Christmas during dinner, he hasn't been put in it. Now I give him a treat and he goes in there to eat it!

I have no idea if he ever had puppy shots or not, I do have the paper work for rabies and parvo shots, but that is it. Does it hurt if they have them twice? I was told he is about a year old.

Thanks for your time and help!