What are the necessary things you need to bring on a 3 day camping trip

Sleeping bag (depends on the weather), canteen (or bottled water), good shoes (if you are hiking).

depends on the trip. but for three days, you can have a lot of fun with just the above.

Change of clothes,flash lights,something to start a fire,food. Have fun & good luck!

Here is what l bring:
Sleeping bag
Tent
self-inflating ground pad
water filter
1 litre Nalgene water bottle
camp stove
cook set
food
xtra socks
first aid kit
hand sanitizer (not just for hands!)
poncho that will cover me while wearing my pack

And a backpack to put it all in, of course.

cover of some kind,food ,water,extra clothes,fire making ,knife ,ax ,must dress for the weather ,insect repellent,common sense is most important

beer

Have a look at this. A similar question and my answer from the other day.

Have fun!

Food, shelter, and appropriate cloths, rain gear, jackets.