Useful co-sleeping tip #2: Get Dad involved.
After Maria upgraded to a toddler bed, she became my responsibility at night. The toddler bed was against my side of the bed so I had the responsibility for enforcing the night-time rules. For a while she was allowed in bed whenever and I put her back in her bed when she fell asleep. Then we moved to a time limit, where she had to stay in her bed (or be put back in her bed) before three a.m. Afterwards she would snuggle up with me until she fell asleep and I put her back in her bed.
Currently she stays in her bed except for a few nights a month so things are pretty loose. Although if she is a squirm-a-saurus, I put her back in her bed pronto. If she is still fussy, I sleep with my hand hanging off my bed and holding her hand.
However, Maria was primarily bottle-fed due to milk supply issues so I have no idea how to handle Amelia's transition. I found this transition to be the most difficult part of cosleeping and the least discussed in the literature. I hope this blog can remedy that situation for others.