The first few months of a job can make a person nervous. Will they fire you after 6 months if you don’t fit in? We all want to make sure to make a good impression on our superiors so that we don’t get a pink slip. But chances are that your boss doesn’t have time to see what you’re doing all the time. He may depend on your co-workers a bit for an opinion on your work. For this reason I believe it’s critical to be nice to everybody in the company you come in contact with. That includes everybody with a kind smile to the grumpy veteran in the corner. It doesn’t matter how good you may be at your job, the boss values the opinion of people that have been working for the company longer than you have.
I found this out when I worked with, honestly, a bunch of idiots. I worked my tail off to prove myself. I thought the boss would see what I was doing and value me above all his other workers. I pointed out what I thought were flaws in others thinking I was winning points. It ended up winning me a cardboard box.
Right now I have a position where a non-manager is showing me the ropes. When it came time for my review, my boss asked him what he thought of me. Luckily we get along great and I got good marks.
Even if you’re not working directly with anybody, word gets around the office about whether the new guy is a nice person or not. Make sure anybody in the office would give you a thumbs up if asked, because they will be.