Before I get into how to establish relationship, a quick tale. Wednesday, during a 10 minute break from acting class I went to get a bag of chips. I saw a Dorito bag with cool graphics all over it. It was an advertisement for the latest version of "Halo" an awesome video game that people go nuts over. I snagged that bag because I didn't realize that it was promotional advertising, I thought that Doritos now came in a new flavor, a "Halo" inspired flavor. Perhaps they are remarketing my beloved and ne'er to be seen again spicy sweet chili? Nope. It was nacho cheesier. Damnit! Watch out consumers, those bags are tricky.
There are a few ways to establish relationship and by doing so, get the focus of of yourself. I will talk about two ways: one is more suited for rehearsal and one is more suited for performance.
For the rehearsal tip, taken an object and stare at it, play with it, manipulate that object in your hand. When you're doing that, run your lines and you'll see how much better you will sound. Your rate, inflection, pitch and dynamic will become greatly varied. Don't just pick up the "Papermate" brand blue ball point pen and go about your lines. Study that bitch. Notice how the prong from the cap eventually pulls away from the pen when it is sheated? Notice how there are two hearts on top of each other in between the words paper and mate? Notice how the end of the cap is thinner than at the beginning of the cap, where the pen first enters? This is how specific I needed to get to get the focus off of myself. You may not need to get this specific, but you'll only know by trying.
Watch an old Marlon Brando flick and notice how he constantly plays with objects. He was a very tactile actor. He was doing that to get the focus off of himself and put the focus back into the scene, and it works wonders.
For the performance tip, I suggest focusing all of your gaze onto your scene partner. This will put the focus on the other actor and will therefore give you less to worry about. When you have less to worry about, your work will succeed. Often times, a film director will tell the actors to take the scene again "just as a throw-away, this one doesn't count." And wouldn't ya know, that is usually the best take. Why? Because the actors are relaxed and therefore have all the focus off of them.