Unsure on how to complete my W4 form

Hey! My wife and I got married in March and had a baby in September of last year, but my wife and I never changed our W4 forms. We both work full-time (salary and hourly), and I am the only one that puts a percentage into a 401k. My wife pays off her student loans as well. How do I go about filling out my W4 form? Does adjusting my W4 mean that we will get more money per paycheck? I really want to make the changes, but nervous that I will complete the form incorrectly or end up owing a lot more.