The IETF defines 'New Participants' as anyone who has participated in less than 6 meetings (onsite or remote) and provides events and other services to help them get the most from the meeting.
There are a number of events specifically set up for new participants during the week. These are advertised both in the agenda and on the new participants mailing list.
The New Participants Overview Tutorial, generally held on Sunday, where an experienced IETF participant presents a general introduction to the IETF. The session covers the structure of the IETF, how to get the most out of the meeting, and many other essential and enlightening topics for new IETFers.
Then later on the Sunday is the New Participants Quick Connections, which is a simple and effective way for new participants to be introduced to a variety of experienced IETF attendees — often working group (WG) chairs — who can help you get more involved in your areas of interest. It is a great chance to meet people, and establish contacts that can be useful during the rest of the week. Registration is required as space is limited.
The New Participants Dinner on the Monday night is a subsidised dinner providing time for in-depth conversation and socializing.
Finally there is the New Participants Happy Hour on the Thursday evening, which is a great opportunity for newcomers to share their experiences and discuss topics of interest with IETF leadership.
The IETF Guides program, pairs newcomers with an experienced IETF person to help you become acclimated and effective quickly. If you are interested, watch for the announcement. The intent is for you to have a call with your guide before the meeting, a meeting during the beginning of the meeting, and check in some time during the meeting, so they can help you with any questions you might have.
All new participants are automatically subscribed to a special mailing list (unless they opt out). This is used throughout the week to keep new participants up to date on relevant events.
The IETF has a YouTube channel which has the previous new participant tutorials. This has recently been broken down into four 15-minute segments which might be easier to view.
It is best to plan to be present the whole week, to benefit from cross-fertilization between WGs and from hallway discussions. As noted, the agenda can change, and there have been instances of participants missing important sessions due to last-minute scheduling changes after their travel plans were fixed. Being present the whole week is the only way to avoid this annoyance. If you cannot find meetings all week to interest you, you can still make the most of the IETF meeting by working between sessions. Almost every attendee has a laptop, and it is common to see many of them in the terminal room or in the lobbies and hallways working during meeting sessions.
As a new participant, don't be afraid to strike up conversations with leadership (people with dots on their badges). If the IAB and IESG members and Working Group and BOF chairs didn't want to talk to anybody, they wouldn't be wearing the dots in the first place! Note, however, that if someone is very busy and you want to discuss a complex topic then they may ask you to send email after the meeting ends.
For a good primer on how to effectively engage in the IETF, read RFC 4144: How to Gain Prominence and Influence in Standards Organizations.