babys blanket

It is more advisable to put your baby to bed in a sleeper. If you absolutely have to have a blanket on the baby, tuck it tightly around and under the foot of the mattress with your baby's feet touching the footboard.  Also you don't want to put the blanket any higher on the baby than up to his chest as that will help prevent him from slipping under the blankets and suffocating. 

Bumper pads are a great concept but unless they are secured properly, there is a risk of your baby slipping between the mattress and the bumpers and possibly suffocating.  If you use them they should be anchored in at least eight places one at each corner of the crib and at least two spaced evenly on each of the sides. There should be a total of 16 ties in all, for the top and bottom.

Mobiles are a nice addition and look adorable but... the caution here is that if you use a mobile as soon as your baby starts to sit up on his own the mobile should be taken down to prevent your baby from getting tangled in it. Also make sure that it has no small removable parts that your baby could choke on.
If your crib is second hand no matter whether you had for a previous child or you got it from someone else check out the mattress carefully.
 Make sure there are no cracks or holes in the mattress covering. Make sure too that the mattress properly fits in the crib. Here again, your child could slip between the mattress and the sidebars or the end boards and suffocate.