An Unique View!

I was recently watching Star Wars:A New Hope on the HBO channels and it has come to my attention that Obi-wan knew exactly what he was going to do on the Death Star when they came out of the smuggling compartments and I think he used a special technique that our favorite fallen Jedi uses all the time.
Force Suppression, aka hiding in the Force.

I think Obi-wan knew he was going to have to contend with Vader on the DS. That's why he hid himself from the Force so Vader couldn't pick up on him easily (but he could still sense him which can be a testament to his true abilities and wouldn't you think that a former student and semi-brother would recognize his former master instantly). He first went to go put the tracker beam out of commission so Luke and the others could leave with out incident. Up to and after the clandestine mission to disable the tracker beam, Obi-wan probably use the Force to hide (or rub their memories of the encounter) from the officers and stormtroopers so they wouldn't stop him yet this usage (coupled with the Obi's distraction with the stormtroopers near the tracker beam) probably tipped Vader off which would explain the scene with Vader and Tarkin.

It was useless for Obi-wan to hide in the Force so he knew had to fight Vader but I feel he headed back to the Falcon to send Luke off and then go fight with Vader. However, Vader threw a wrench in Obi-wan's plans and waited for him to come to him right outside the Falcon.

Obi-wan distracted Vader from Luke so they could get a way. Right when Obi-wan sacrificed himself to Vader, he cemented Luke's "hatred" for Vader thus rendering Luke from ever turning to the Darkside before his "trial" with Vader and later with the Emperor.