You might be able to find out if you use Google's Web Master Tools (which has been recently updated). Their diagnostic section is pretty informative, and now includes graphs for loading times - which is supposedly a ranking factor in the serps.
First of all search engine basically Google checking robots file in web pages after that .htaccess file and then read web pages title and Description tags.
Yes, you are right when Google bot comes to your website at first its see the http header tool then robots.txt and .htaccess file after that Google bots follows the title and Meta tags for particular webpage, that is the only reason that webmasters create most relevant title and meta tags for their website.
Nice information. agreed! yup Google Crawler first Visit your url and Header Tags. Thats why In SEO point Of view in On Page SEO Header tags are very much important part.