Seems like something different works for everyone, but here are some things that help me:
Wishgarden Herbs makes tinctures that are safe for pregnancy, and I've successfully used the allergy and cold formulas. Instead of a neti pot (too messy and I don't want to bother boiling water each time), I get a saline solution spray can from the pharmacy and use it in the shower to irrigate my sinuses every single day. I also use an air purifier and try to wash my clothes more often. I know the latter sounds weird, but it helps for any items you tend to re-wear without washing each time, like jeans or hoodies. If you've spent a high pollen day outside in your favorite hoodie, you'll continue to breathe that pollen in every time you wear it unwashed. Same goes for your hair, too.
I had a good routine going with daily nettles tea and local honey, but that's over with the pregnancy. Everything's dead from the heat right now, but I'll have to see how I do without the tea when the pollen makers come back to life this fall.