Try not to skip
I know this isn't exactly step one of skipping class, but I have to caveat this post with my own opinions about skipping. Law professors go over a lot of information in each class so you really are missing out if you miss class. So really, the best way to be able to skip class for something important is to go as much as possible when there's not an important reason to skip.
Read the syllabus
I know you already read your syllabus at the beginning of the year, but double check to make sure you know exactly how many absences you get! And make sure you read it carefully – does it say 4 absences and then your grade gets docked, or your grade gets docked on your 4th absence? See, this is a big difference!
Try to convince yourself to go to class
Not to be a mom, but sometimes you don't want to go to class and staying in bed all day sounds amazing and on those times you need to give yourself a kick in the butt and make yourself go. If you want to read about how I would end up going to class even though I wanted to skip, check out my 1L in Review post.
Don't use up your absences too fast
One thing that helps me go to class is that my professors generally allow 4 absences and there's about 4 months worth of school, so I try to limit myself to one time a month. Because of this, I usually save my absences during the first week or so of each month juuuust in case I end up needing it more later in the month. Seriously, the worst thing that you want to happen is have something big like an interview that you need to skip to get ready for but you can't because the week before you were hungover or something.
Keep track of the days you miss
In all of my classes so far, attendance isn't "for a grade" but your grade is negatively affected if you miss too many classes. I highly recommend that you keep track of what classes you miss and on what days so you don't end up missing 5 MWF classes because you thought you remembered one of your absences to be on a TR day. You can see an example of how I use my planner to keep up with these in my The Best Planner for Law School post.
In college if you missed class, it'd be fine because you probably wouldn't miss anything important but that's no longer the case here. By the next time you go to class, you'll be completely confused and then now you're behind. As soon as you can, try to do the readings for the class that you're going to miss so that you're not stuck doing double reading (which could be almost 100 pages!) for your next class. It also wouldn't hurt to try to check a supplement like Quimbee or something to try to watch a video over what you missed.
Don't skip the hard days
If you do your readings and are completely confused, then really you should go to class unless there's an emergency reason for why you're skipping. Most people have the light bulb go off as someone is explaining it to them. Also, make sure that the day you're skipping isn't anything important like the day a professor has a quiz or a handout planned.
Email your professor
If you do have an important reason to miss, it is just courteous to email your professor and let them know what class you will be missing and why. Since it's super common for law professors to cold call during class, this just lets them know to not bother calling on you that day. I wouldn't recommend asking them to tell you what you're missing in class because they'll probably just be annoyed and tell you to ask a friend. But I do recommend you ask them to let you know if they make any special announcements or anything like that. Here's what I said once —
Subject: Monday's Wills and Trust Class
I just wanted to let you know that I won't be in attendance for Wills [here you can specify either your section or class time just in case your professor has more than 1 of the same class] tomorrow because I have a summer internship interview and the only time that they would be able to see me is during this class time. I've already read pages 253-277 for that day, but I would appreciate it if you let me know I miss any important announcements from class. I'll see you on Wednesday!
Ask for notes
The #1 rule at the beginning of each semester is to make sure that you have the number for at least one person in every class that you have. Luckily this is easy as a 1L because you have the same people in all of your classes. Text them ahead of time if you can letting them know you won't be there and ask them for a copy of their notes. I say do it before instead of after class because for me personally I take kinda sloppy notes but when I know that someone else will be looking at them later, I'll make sure they're more easily understood.
Don't panic and think that they won't help you out or will try to sabotage you in some way because really law school isn't like those crazy rumors and if they do try any of that crap then cut that person out of your life because it takes a village to do well in law school. But really though, most decent human beans won't mind taking a picture of their notebook or copying and pasting their notes into an email for you. They'll have your back because they want to know you'll have their back if they ever have to skip too.
Also, make sure that after class you double check with them after class to see where they're at in the readings. It will help when you come back to class if you know whether your professor fell behind or got ahead on the syllabus.
Check for slides
I know this sounds like a lot, but it's just because law classes go over a lot of material in one day and if you're not being this extra then you could start to fall behind. If you do the readings on your own, get a friend's notes, and check the slides, then it should be almost like you didn't miss at all. I suggest getting the notes and looking at the slides because sometimes one will explain what you read in the other better. For example if in the notes they have the answer to a hypo problem that your professor went over, then reading that hypo off the slides is a must. Remember that you're trying to get a complete picture of everything that was covered that day in class.
I know this is probably overkill, but being in law school makes you take all of these extra steps so you're not screwed. And although I said to try not to skip when you can, remember that you do have these absences and you shouldn't feel guilty for using them! Even if it's just because you're feeling stressed and need to take a day off, that's ok! Honestly sometimes I realize that I haven't used my monthly absence so I'll decide to take a 3-day weekend and I look forward to it all week 😊
Related: It's Time for a Lazy Day