I'm not sure there is a way to safeguard against useless items. I'd just register what you think you may use and then you can either regift or return.
What I found useless were:
1. swaddle sacks/woombie - I have a baby that screamed and cried when she was swaddled. I still have unopened ones that I will be regifting.
2. burp cloths - Julie rarely spits up so we just use a blanket to wipe her face. She gets a new blanket everyday so why not make use of it.
3. soothie pacificers - didn't work for us, she couldn't keep them in her mouth.
4. diaper changer cover - my baby loves to pee and poop right when we take the diaper off, it was and is still easier just to put a towel down or use a disposable changing pad. We use the burp cloths to clean up the changing table sometimes
5. diaper caddy - never had a place for it.
6. graco lullaby music player - i would really need about 5 of them for it to work...we never seem to be where it is, so it is rarely used.
7. bottle warmer & wipes warmer - my brother gave me theirs but it was easier just to warm up a washcloth and use a cup of water
8. sleep gowns - weren't my style, didn't like personally
9. bibs - I don't care if an outfit gets dirty as I feel that is what clothes are for. Also for feeding (cereal right now) we get the disposable bibs...much easier IMO.
10. sleep wedge (that prevents rollover) - didn't need it for our child
11. crib sheet saver - maybe we are just clean freaks but we wash her sheets, so what is the point.
12. diaper bag - I find it to be a pain. I have a child who likes to be held when we go places, so trying to hold her and carry a bag that is constantly falling down, ugh! I got a canvas bag that I can wear across me (for $5 at Target) and I put her stuff in it and it works perfectly.
I'm sure these items worked wonders for others, but not us. You just really never know what your preference is going to be or the personality of your baby.