Basically everyone need a mobile phone specially android now a days. If you want to upgrade or even planning to buy for first time read this post
Specialization why do you need your mobile for for main purpose all mobile has almost everything so you have to decide what is the main reason is it camera or watching movies playing 3d games or just for business purpose( requires large battery capacity)
Storage now a days with apps and media storage storage is something you have to consider seriously there is some phones that can’t allow to expendable storage in that case you have to consider buying that model too
camera setup now days dual camera is very famous if you like photography dual camera setup is a must
battery for certain you need at least 3000-4000 mah average
most important processor+gpu and ram
there is also many more things like usb type c support otg support quick charge facility if you have any question or needs info regarding any phones do comment .