[sueby]

I would agree with something from everyone: 10-15 minute warm-up to give late-comers a chance to join in, then new vocab and grammar followed by activities. I also agree that it's the student's responsibility to turn up for class on time. I would suggest putting up a sign on the door of the classroom warning late-comers not to interrupt class if they arrive over 15 minutes late, or something similar.

[beschwar]

I hope this reply finds you well and in positive spirits.
#1. Stay Positive
#2. Don't Take Things Personally, AT FIRST
#3. Foster Team Play
#4. Foster Relationship Mentality
#5. Impress Upon Students the Need for One Anothers Mutual Support of Each Other
#6. Have, "THE TALK", which is a t/o conversation (have another teacher, friend, administrator; talk with the student in a motivational and supportive way, the first time around)
#7. Continue to Impress the Importance of Family Atmosphere and the Reliance Each Member Places on One Anothers Presence, on Time, and on a Regular Basis
#8. Stay Positive
#9. Force Peer Pressure
#10. Inforce Financial Penalties

Stay positive and just keep having fun. Stay interested in all, paying particularly close attention to those that seem to be uninterested back.

Go Get 'Um Tiger!!!

[kisito]

Really nothing you can do. The test is on your patience. You need to keep calm and be flexible with your lesson plans. I had a class of students like that. Their company paid for English lessons which they didn't want to take. To them it represented extra working hours. So I either had absences, late coming all the time or students who were hard to motivate. It tests your nerves.

[jakda]

You can always change your lessons to accommodate those who turn up late, but it isn't fair on the other students. Talk to them individually and explain that it affects others you, and the other students who turn up on time.

They may have reasons for turning up late, but if it is just down to lack of effort to come to class then it isn't fair. It is always harder with adults as calling parents makes a big difference. But beschar offers good advice. Keeping a good relationship within the group makes it harder for those to break the cohesion. Let them know that.