Preventing Cross-Pollination

Preventing Cross-Pollination

I know it's a little early for this, but I was wondering if and how you guys who save seeds keep plants from cross-pollinating when you want to. I'm planning on planting several varieties each of tomatoes, squash, corn and melons, and I don't want a repeat of what happened to me last year. Suffice it to say that zucchini and crookneck squash should be cooked together, not allowed to combine into one rock hard super-squash. Similarly, I want my cherry tomatoes and slicing tomatoes to keep their genes to themselves. So, what should I do? Tie little paper bags around unopened flowers and pollinate them myself? Plant each variety far away from others of it's species? Something I totally haven't thought of?
Looking for advice on canna & arisaema.

Looking for advice on canna & arisaema.

Our Garden

Our Garden

Splitting a Rosemary Plant?

Splitting a Rosemary Plant?

My musings on rain barrels and catchment systems

My musings on rain barrels and catchment systems

Regarding variegation

Regarding variegation

My room!!!

My room!!!