Location, location, location
Include location specific hashtags, especially if you are a local business/service. For example if you are a photographer based in Vancouver, try using #vancouverphotographer #photographycanada etc. This will help your potential client find you on Instagram while they're looking for a business/service in the specific location. If you live in a smaller town, you can try tagging a larger city closest to you to expand your reach.
Keep it relevant
Make sure your hashtags are relevant to your business or service you provide and also the audience you want to attract.
Switch it up
Don't use the same hastags for every post. Create 5-8 different hashtag groups and keep them saved on your phone notes to copy & paste easily. I would also recommend Planoly or a similar post planning app that will let you keep your hashtag groups in one place.
You can use all 30 hashtags if you want. There's no magic number, just remember; quality over quantity is always best.
Not so obvious!
Try to avoid using spammy & overused hashtags; like: #art #design #photography #likeforlike as there's a little chance of being seem and reaching the right audience. Niche down instead. Based on a previous example as a Vancouver photographer, assuming you are a portrait photographer, you could try using #vancouverportraitphotographer #portraitphotographyvancouver