Saftey tips for Co-sleeping?

I was wondering some saftey tips on co-sleeping with a newborn? I don't use a snuggle nest or anything, he hates those. I was wondering if there are some other tips out there I should be aware of, I am a first time mom so please be nice.... :D I only put him in the bed with me for a 3 hour nap during the day. He is 3 weeks old. Thanks.