different shipping rules for different products

If I have some things that can be shipped free and some that are heavy and therefore always have shipping.

Can you set different shipping rules for different products? Seems yet another obvious question but I can't figure it out. Thanks

What do you do when someone buys a free ship product and a paid ship product together?

I carry many products. Some ship for free because they are small for example reed diffusers are small and ship for free.

However, I also stock much larger items like televisions and such that have an associated shipping cost.

Obviously global free shipping on price doesn't work and it also doesn't work on weight because you could order 500 diffusers to hit a televisions weight but would still get free shipping.

I don't know if that is any clearer. Currently I use the free ship module and have a disclaimer about shipping being added. But what would be far better is to define certain categories or products as always free shipping or the exact opposite meaning have all items cost but some are specifically coded as free. Works either way.