About Which Strings Need the Barre? – Quick Practice Tip:
Here's another tip that goes along with that first one!
When I'm playing an E-shape barre chord, the only things that the barre really has to cover are the top two strings, and the bottom string. The highest and the lowest.
When I'm playing the A-shape barre chord, the only strings that that barre has to cover, is the highest string and the lowest two strings.
So, remember that it can curve up a little bit in the middle because you have other fingers playing those strings.
Focus your attention on the outsides and make sure you have your finger shifted to get the strings covered to get the clear tone you're looking for.