Call the Keeper! 

Do NOT call all exterminator when you see a hive on your property, and do NOT go spraying them with Raid or the like.

Most of the time when you see the swarm, they are actually just relocating for the spring and just trying to protect their queen. They will be completely harmless, and will move on when they are ready.

If you feel the need to, call a local bee keeper to make sure they get relocated safely. friendlylycanthrope

Habitat for Bees! 

Entomologist here. First, remember that honey bees are not native for those of us in North America. They are actually livestock. That means keeping a bee hive is not going to save the bees.

What's more of a concern are native pollinators they are usually solitary bees or ones like bumblebees. The big thing for them is habitat. Some are ground nesting, but others like to nest in debris like leaf litter, hollow sticks, etc. If you just have a lawn that gets mulched all the time by mowing, etc. that's not really helping them out.

Whether it's honey bees or native bees, food sources are the other main factor. Many bees have troubles because they don't have a consistent food source throughout the growing season. If you have just one type of flower that blooms in July with not much else, those bees are going hungry. You want a variety of flowering plants that also bloom at different times.

There's no silver bullet really, but that's about as close as it gets with maintaining habitat and not just having bee food deserts, especially in cities. where_are_the_grapes

Damn the Grass! 

Grow native grass, plant native flowers, stop spraying pesticides. Regular grass is damn stupid. TabascohFiascoh

Not the Dandelions! 

Plant flowers/plants that are native to your area. That's really important! See what grows naturally around you.

Don't mow down dandelions in the spring. That's the first food source bees have access to.

Make a sugar water pitstop for them. Making faux nectar just like we do for hummingbirds.

Support farmers! Farmers means bees pollinating and many of them keep hives just for this purpose.

Start a hobby hive if you can.

If you find a hive that needs to go, don't just destroy it! Call around and you should be able to find someone more than willing to collect it for relocation.

Buy local honey and wax products. Supporting bee keepers supports happy, healthy bees! Gloeee

Flourish the Flowers....

There are a lot of potential contributors of colony collapse disorder and a lot of debate over what's really causing the most damage to our bees. The average person has control over two things that could benefit bees: their yard habits and their honey habits.

The easiest thing to do to help bees is buy honey locally. The stuff you get in the store is terrible compared to the real product, and if you buy honey from local beekeepers, you're not only supporting that hive, you're also helping your allergies.

The other thing you can do, and the hardest thing for many people to commit to, is to ditch the 'ideal' version of a yard society has pushed upon you - a yard made of one homogeneous plant species (completely unnatural). This perfect, green lawn takes a lot of fertilizers and chemicals to maintain, the second of which is harmful to insects, e.g. bees, and minimizes a bee's natural food sources: wildflowers = flowering weeds. Let the flowers flourish. You can plant some of your own, and that will help, but native flowers are what native bees will utilize the best. Def_Not_The_Same_Guy

On the Decline.... 

Stop trying to save honey bees specifically. They are a symptom of a much larger problem, native bee population decline.

Honey bees are actually an invasive species, and are really only beneficial to agricultural pollination. Native bees are important for local ecosystems and local flowering plants.

Best you can do for them is plant local flowers, try not to use pesticides, and try as best you can to push for climate conscious initiatives. There are no species specific pesticides, any claiming that they just kill the bad stuff are lying, and climate change is affecting things on so many horrifying levels. HovercraftFullofBees

Check-In! 

I have actually been to a "bee hotel" and I kind of want to make one myself. Essentially what you do is get multiple pieces of wood and stack them. You drill different sized holes in these logs and plant flowers that attract native bees. These bees then live inside the holes and have places to live! They're completely harmless if you don't bother them (I do take precaution to people with allergies, obviously lol). They look pretty cool if you put some work into the design, and they help a lot with keeping bees alive. DanceGrape

Picnic Love! 

Not kill them when they get into your house. Not kill them when they're around your picnic area. Not kill them when you think they're out to get you. Unless there's a swarm who thinks it was you who disturbed them, don't do stuff to them. miggy07

Not a Wasp!

Don't mistake them for wasps and kill them. TheJadedSF