Muscle in the forearm, rib, loin, hip,stifle quarter and a wide base. If your young steer does not show potential in these areas when you buy him there is a very good chance he won't have it when he is finished.
Structure correctness look at the feet, straightness of the legs, and nice straight flat back with spring to the rib.depth of body, uniformity of body depth and chest width.
Now that has been said; you must have a picture of what you are looking for in your head and go into the pen of 75 to 100 head or more of cattle and pick your steer.
The way I do this is to pick 12 to 15 head that fit my list and chose from those; this only takes me about two or three hours; my cattle producer is very good to me.
I think the most important thing to look for is a steer with as many great qualities as possible, and the most important of all is a great disposition because if you can't show them, and you can't touch them, you can't judge them.
So that perfect crazy steer that runs, jumps, puts his head in the air and paws the ground; you run don't walk away from him NO matter how perfect he may look; for he will most likely be crazy in the show ring.
The last tip I will give is to pick what you like, and remember that every judge has their own list of qualities of what he or she looks for in a 4-H show steer and there is know way of knowing what is on their list.
One last thing the Producer knows their cattle so talk to them and always take in consideration everything that they have to say, you are show casing their cattle and their brand is on your steer for all the world to see.
Show your steer with pride and confidence and no matter what the out come you can leave the ring knowing you did your best.
I myself have not had a Grand Champion Steer YET; but I have made it back to the championship round every year.
I do my best and that's all I can do.
Good Luck