Update your pages regularly: You must have to frequently add new, original and quality content on the website for this.
Server’s Uptime: If a site is down for a long time, the crawlers reduce the frequency of crawling for that site. So, host your website on a reliable server with good uptime.
Create Sitemaps: You can submit sitemap of your website to make your site discover quickly by search engine spiders. In WordPress, you can generate dynamic sitemap with Google XML sitemap plugin and submit it to Webmaster tool.
Avoid Duplicate Content: The copied content tends to reduce the crawling rate as using plagiarized material is against the guidelines of Google. So, always provide new and unique content.
Reduce site’s loading time: The loading time should be less as the crawl has a limited time and if it spends too much time on big images included in the content, it will have no or less time to visit other pages.
Build more links: You can build more backlinks from regularly crawled sites. Interlinking helps search engines to crawl deep pages of your site. So, whenever, you create a new page add a link in your old related pages to your new page.
Use optimized images: The crawlers cannot read images directly so always use alt tags to provide a description that search engine crawlers can read and index.