It comes from the factory with the tie downs attached to the cross bar on the frame, just in-front of the head, where the engine guard bolts-on. But that only works if your D-rings are placed where the tie-downs won't rub on the fender or lower fairings (if you have them).
When traveling to destinations that are +1,000 miles away and the wife is accompanying, I have to trailer due to my wife's back problems. My trailer has a roll-on wheel chock, so my primary need is for the tie-down to pull the bike forward to lock-in the front wheel. I use a tie-down attached to the rider floorboard mounting bracket to create that force, then use a second set of tie-downs on the saddlebag guards, as close to the lower mounting bolt as possible, again pulling the bike forward (as opposed to just trying to secure the rear-end). The lower side of the saddlebag guard has a horizontal cross bar that keeps the tie-down from slipping down to the outer curve of the guard where it might create enough pressure to bend the guard. In both cases, I use tie-downs with the spring loaded latch on the S-hooks so that they don't fall-away if the trailer has a hard jolt. If your tie-downs don't have the latch, you can tape then to accomplish the same effect. Don't ask me how I learned about S-hooks slipping off...it's still too painfull to discuss in public.
On my Ultra Classic and Ultra Limited, I had installed the tie-down brackets on the front forks. Those work really well, but cannot be mounted on the Road Glide due to the fixed faring. Darn shame.
Some folks seek the comfort of the straight and narrow. Me? I prefer the twisted road.