Pretty much all the dogs I have been with behave in a similar manner.
It starts with sniffing my croch area. As a guy, I am not sure what exactly attracts them to it, I do shower everyday and practice proper hygiene, but I will take that as a sign to see if they are interested, or just you know, being dogs.
I will pet them and then see if they will let me touch them, if they are not ok with it, then I leave it at that, but if they are they will usually turn all the way around and "flag", even if they are not in heat. It's not as aggressive of a flag, but they still try.
On a rare occasion I had one female who would just immdeately lay down and roll on her back with her tail wagging uncontrollably as soon as I walked into the room. Started with belly rubs, and then slowly worked toward her vaginia to see how she reacted. She was 100% submissive and I could have her anytime I wanted.
One of my last two females, the oldest, absolutely loved giiving me oral, and would just completely go nuts when I cam while she was licking me, or when I came inside her. The last one, she only liked to be masturbted and never let me fuck her, but that was fine by me, she would do this little growl when she came, it was so cute. She was the most adorable and lovable dog I have ever owned, had a personality like no other, I really miss her.