Ok, I need help!!!

Not too long ago, I did a clean out of my clothes but not really!! A few things went but not as much as I would have hoped for. Now, my drawers and wardrobe are bursting at the seams again and I want to do a huge cull but I look at something and think, I might wear that again!! But I probably wont end up wearing its just hopeful think you know?
I have a lot of clothes that I bought for work, but I don't work any more so these I will see if my sister wants them so thats not a problem. Its just the other stuff...

So, whats the best way to cull my clothes?!! There are things in there that I bought seasons ago and things that I maybe wore 6 months ago. I know that those items should be easy to be rid of but I still find it difficult...