1. Interact, like, comment
But let's start off with the following: don't overdo it. If you're gonna comment 'hi I like your feed' on every photo, you're not gonna come across as if you mean it. Be sincere! Drop a comment every now and then, like a few photo's and make sure you react to comments on your own photos. Sure, copy-pasting a comment is much easier, but people will see right through those standard comments. Put a little effort in a more personal message and people will genuinly like to check out your account and follow you back.
2. Post no more than 3 times a day
Bloggers in particular often talk about 'posting schedules' and perhaps you also post your photos at certain times in hopes of getting more likes, comments or followers. Especially on Instagram, this won't have much effect. Instagram's algorythm decides what your followers will see first. That has got nothing to do with the time or day you post photos. It's got everything to do with how iteresting and relevant Instagram thinks your photos are. So spamming is not going to work. Especially not when combined with too many hashtags ;) Post a photo whenever you feel like it, capture it with something relevant or question to get a discussion going, and follow point 1!
That is all you need to do to effectively gain more interaction on social media! More genuine likes, comments and followers guaranteed.