In my belief, the best (if not the only) way to get ideas for a blog post is to consume a different type of content created by others.
As you are actively engaging with content, you can easily discover topics or keywords that you could discuss in your articles.
Here's what I do on daily bases to collect ideas for future blog posts:
follow other blogs;
- subscribe to newsletters of these blogs;
- keep track of what my competitors are posting;
- join different communities and forums (GrowthHackers, Reddit);
- join groups on social media (LinkedIn, Facebook);
- use StumbleUpon to discover new content;
- communicate with my colleagues: ask what are the questions they receive from customers frequently;
- follow what influencers speak about;
- use Hubspot blogpost topic generator;
- research most popular articles by keywords on Buzzsumo;
- look for inspiration on Quora;
- go out and meet different people.
I'd also suggest you create a separate document or have a page on your notebook where you write down all the ideas coming your way.
Even if you have what to write about, you can come back to that list when you think you are out of ideas for your next article.
All the best...!