Where you post your classified Ads ?

Hi all, I’m newbie here and looking for some help from you people. I hope will support me. Where you post your classified Ads ? What you can recommend for me ?
I’m looking for a good place in UK where I can post classified, buy/sell Ads in free. I got uk free classified ad when I was searching for this but still want to know from you.

Please suggest me.

Thanks!