At 18 months we moved ds into a toddler bed with side rail, stair gate on door. Routine was:
5.30 dinner
7pm bath
7.30 pjs and play in room
7.45 books and breastfeed
8.00 asleep.
Then he would come in to bed with us at around midnight when he woke up.
Now have a 12 month old co sleeper and her routine is:
6.30 upstairs
6.45 in bath
7.00 out of bath and in pjs
1 story and breastfeed to sleep on lap on sofa, asleep by 7.30, comes up with us when we go.
Would agree with no tv after dinner certainly, maybe a cut off point at 4ish, and no extended play after bath.
The thing we've found best since having two to coordinate, is keeping each schedule to no more to an hour. This has made a huge difference in the last couple of months, we used to faff about a lot more, they have both been going to sleep like clockwork since we made the timings tighter.
At 12 months I can't let dd sleep past 3.30-4 in the day, I imagine at 18 months that would be more like 3. I think a good rule I've found is 4 hours between last nap and bedtime. Less than that and you struggle, more than that likewise.