Pretty simple. Those qualified to do Ijtihaad do ijtihaad and the laymen do Taqleed of the scholar/s whom they trust.
Sorry what I meant was to ask, how exactly should taqleed be done, I mean, there's this Afghan man in my masjid who comes for every salat, but he doesn't put his feet next to his brothers' feet, he is doing taqleed but is his taqleed correct. Why does he remove his feet everytime we put our feet next to him?? What's his proof that it's wrong?Taqleed - a layman follows a scholar he trusts.
Ijtihad - a scholar follows the best evidence according to him.