At larger properties, where there is a busy lobby that usually includes some time of eatery, bar and/or coffee shop I just book as a solo traveler.  There's so much going on that traffic to one room is not going to stand out so much.  

For smaller hotels, I generally book as 2 people and ask for 2 keys.  If they ask, "is the other person in your room checking in with you" I reply that his flight was delayed and I'm unsure if he'll even make it in.

On the rare occasion that they state every adult in the room needs to be registered, then I just repeat the above story that my roommate may or may not show up and tell them that if he does make it in, I'll have him register with the front desk to get his key.  All of the above said with a smile, of course.  

Whatever they have to say, always nod and smile.   Do not question their policy or debate the issue.

I'm all for standing one's ground and asserting your rights as a hotel customer, but IMO, it's just not worth it when you're there to work.  

 
xoxoxoxoxo