When you start a new job you have to expect a few blisters along the way. The key thing to settling in is trying to understand as much about the company you are joining before you start. Through the interview process ask questions that are relevant to what matters to you and what you are looking for too. Speak to people who work there or have worked there in the past if you can on a casual basis to get a flavour of the culture.
Once you walk down the corridors of the new job, build relationships within your team and try to add value from the offset. Be friendly round the office, introducing yourself to people in the communal areas especially even if you are naturally shy. The more questions you ask, the more enthusiastic you are, the easier it will be to break into that new job and settle in.