(This list consist of hypothetical suggestions and doesn't imply or admit that ANONYMOUS writer has done any one or all of them)
1. Sleep
Depending upon the teacher & the location you can do head down ,head-on-friend's-shoulder or good old fashioned sitting upright sleep. (The writer admits to being terribly inept at open-eyed sleep but the masters of craft should opt for that)
2. Facebook/Instagram/Snapchat/Twitter
The long news feeds seem much more exciting in the class than at home. And if you have earphones Snapchat also offers a delightful option. (All this if you have wi-fi or 3G)
3. Episodes/Movies
It is the most fun option but can also prove dangerous because you can get too involved (and may miss teacher coming to you.)
4. Books
The writer has hypothetically tried both physical and electronic options and most of the novels he/she has read in past years have been "not at home"
5. Games
You can opt for Need for Speed ( the writer recommends Hot Pursuit and Most Wanted) , Plants vs Zombies, FIFA or good old Candy Crush. (Here the writer strongly urges you not to send Facebook requests). The writer may or may not have been playing Candy Crush for years with breaks in between.
6. Annoy your friends
This is a viable option if battery of your mobile is too low or your friends are being just too damn serious.
7. Replying To be replied-texts / Whatsapp / Emails
The boring texts you have to reply but are still delaying (like from your old acquantinces or distant friends) can be adequately replied.
8. Selfies
This one is from the writer's friend who likes to note down most of the lectures and while is a good option for 5 min, I don't know if it's viable for 45/50 minutes.
9. Test/ Substages/ Ward test preparation
It is a very good option if the said test is on the same or the next day.
10. Make "Observations" about the teachers's styling
It is a good past time and if the teacher has particularly good fashion sense you set some styling options too.
11. Just gossip with your friends in a LOW voice
(If the teacher doesn't mind a little buzzing ) The writer here admits hypothetically that he/she finds it a little less respectful and only uses it as a last resort specially because of writer's tendencies to speak relatively loud or whisper too low and to turn his/her head to the other person (that alone will probably be the death of the writer)
12. Write a blog/ story/ poem
This is not any admission that this was written in a class though it is strongly hinted.
13. Listen to the lecture for a change
A few of the teachers actually are both brilliant and good at teaching so if it seems important enough you can try it. The writer has tried it some times and only regretted it a few.
(In our case , as teachers like to point out frequently, God forbid kill our patients)
Note: This blog isn't meant to encourage not listening to lectures. And all ideas should be tried at your own risk.