Congratulations on getting your new job as a software engineer! Your employer and team are happy to have you join them. Here are some tips for the first few weeks to help them feel like they made the right choice in hiring you.
Learn what the work time expectations are for your job -- even before you start if you can. The norm for a full work day is 8 hours. Usually that doesn't include the time you break for lunch unless specifically stated. A lot of people work longer than this -- because they enjoy their work or have commitments to meet -- but a smart employer won't mandate long hours because that is counter-productive.
When starting a new job, work at least as long as your teammates. If they work 10 hour days, you might not want to do that long-term, but certainly don't be cutting out of work after 7 hours on your first day to beat traffic or something. As you gain the trust of your team, working hours can be more flexible and you can pattern your day for your own best productivity and work-life balance.
It can take a little while to get integrated into the flow of tasks that need to be done. If you don't have a specific assignment, you can at least make yourself more valuable by learning about the software your team is building and practicing with the technologies it uses. It isn't time to rejoice that you can binge watch Netflix or catch up on PewDiePie.
If you're in a meeting be present. Unless you are using it for something directly related, your phone stays in your pocket and your other devices are set aside. At first, there will be a lot of things happening in meetings that you don't understand. Rather than tuning out, figure out questions you can ask (either during the meeting or later, as appropriate) that will help you ramp up. Over time, if a meeting seems pointless, you can:
On a new job, the volume of things to learn can make your first assignments seem daunting. You'll likely run up against something that roadblocks your progress. Balance wrestling with the problem against being stuck for a long time. You don't want to run to your teammates or mentor with every challenge, but you also don't want to spend hours on something that could be resolved with a little help. Have you Googled for a solution? Read any documentation there might be? Clearly articulated the problem to yourself (or your rubber duck)?Experimented with some possibilities? If you're still stuck, get some help.
Someone else may be better suited to do a task than you are, but don't be too quick to give up and go looking for something else. If you can work through a challenge, perhaps with someone's help, that will make you all the more capable for future tasks.
If your coworkers invite you to lunch, go with them, even if you've got some great left-over lasagna waiting in the fridge. You might not want to spend the time or money going out a lot, or have other midday plans, but early on, take advantage of chances to get to know your team.
Don't wear headphones the entire day. And probably not all during the first month of a new job. After that, if you need to block out ambient noise, or music helps you focus (and I mean for real, because multitasking is a myth) then it is fine. Just don't hide behind them and cut yourself off.