You must ensure you are using the very best content that user like. To make sure you are, use the viral content checker to see if your content is as good as your competition. Then make sure you are using the right hashtags when posting. Once you have posted make sure you engage every day with your followers as Instagram boosts account that do this.
Not every post will go viral so you should try to do this every day to give yourself the best chance and to test and learn what works best.