When opening a new site for search engine crawl, should the site contain content (posts and articles) from day 1, or is it better to open the site for search engine crawl and than post the articles every few days?
If I were you, I would launch the site with some articles and news (for example, two of each) and I would publish some new articles and news every days for a moment to launch the site and quickly attract visitors.
Once the site is launched, you could publish some articles and news a little bit less regularly (once a week for example) to continue to attract visitors and search engines bots. But pay attention to publish regularly because search engines and visitors like fresh content.
However, these technique is possible only if you already have a set of articles and news ready for publishing.
Otherwise, even if it's a good practice to index the site as soon as possible (to seal the age of the site), it's also recommended to have some content to provide to search engines bots.
Definitely post some content on the website before the launch. If you post news and blogs don't forget to use tags. A great way to start of is to describe a bit of your site, what it is about and what kind of content will it provide. Crawlers collect data from all around the webpage because of that you might wanna to take a look at SEO( Search engine optimization ). As mentioned before if you can have a few posts written but not posted, that way you will attract more traffic in the beginning.
Definitely have content before introducing any search engine to it. Search engine companies want to see users have a good experience on a website and the more that happens, the higher the website is ranked in general.
Having no content when having search engines involved could not only make your ranking drop, but you could possibly end up with some penalties which may require you to fill out a form or two indicating what you did to improve your site and why it should be reconsidered for indexing etc.
When you have a few well thought out articles ready (I suggest at least 20), then create a sitemap that lists every URL on your site and submit that to the search engines you want your site to be listed on and wait about a few days to see what happens.
Also, adjust the crawling settings in webmaster tools that each search engine provides to make sure they are crawling your pages very often at first.