One frequent cause of backups is that a root from a tree or large bush has grown into the pipe. If that's happened to you, you'll need to dig up the clogged area to sever the root and then repair the pipe, or if it's a porous drain pipe, wrap it in a landscaping fabric.
As Tester says, use a snake to see what you can find. You can also measure the distance until the snake gets stuck to get an idea of where you need to dig. Pay attention to any bends you feel the snake making on the off chance it isn't a straight run to the front.
Once you have an idea from one side, I'd fill the drain up with water on a dry day and see if you can find the outlet. Then try snaking from that outlet as well since the clog may be a long one from sediment building up over time. Again, measure the distance, and now you'll have an overall area to check.
You are correct that floor drains do need to be monitored and occasionally the trap refilled with water.
So the first thing to check is that your floor drain actually has a trap. The way to do that is to slowly pour water in to the drain. You should notice the water level rise and stay there. If the water disappears quickly then it's likely you don't have a trap.
Provided that the drain does have a trap, the next thing to figure out is why the trap is emptying so quickly. A common cause is something wrong with your vent stack. Problems can range from a blockage, to an improperly vented drain elsewhere, to no venting at all.
A good way to test your vent stack is to flush each toilet one at a time. Enlist a helper and keep an eye on the water in the trap. If one toilet causes the water in the trap to move significantly or drain completely, you have found your problem fixture or vent stack. Fixing this could be as simple as running a garden hose up to your roof and down that vent stack to clear the blockage.
If climbing on the roof is not for you, then a standard house-call charge from a plumber will likely fix it, and that's not usually too expensive.
But if a fixture is incorrectly plumbed or inadequately vented, that can get pricey.
Best Answer
Well, as long as it does not go into the U-bend where the water trap is (prevents smalls coming up) then it will be fine.
I always make sure it goes in at least 6" as I have seen the force when it starts pumping to push the hose out - leading to some clearing up, one way to get a clean floor though :)