Google updates their SERP daily.
Some people still think that Google rolls out changes in large batches that cause major ranking shifts. We used to call those large batch changes the "Google Dance" because while the roll out was taking place you could see different search results in different locations and the SERP would change with every page refresh.
The days of the Google Dance are supposed to be long behind us. Instead, they roll out changes to the index every day in hopes to have fewer disruptions.
For larger websites this means you have a better chance for your new content to be read, indexed, and appear in the SERP within 1 day. Changes to your Google Places account or Merchant Center will appear in the SERP within a few hours.
After changing pages on your website, you should check the Google SERP every few days to see when the changes take place. You have to give Google some time to find the changes on your site and roll them out in the results.
The SERPs also have a little magnifying glass icon that allows you to see a preview image of the website before even clicking. You should watch the preview image too. The preview images update at a different speed than the SERP. Sometimes they even update before the SERP does.
Another way to check the progress of your website indexing is to look at the Cached date for your page in the SERP. Most of the results on the SERP have the word "Cached" in light blue at the bottom right of the listing. Clicking that will show your web page the last time Google read it. Look at the top of the cached page to see some interesting details in addition to the cached date.
The last nugget of information to share with you today is that Google sometimes rolls out changes as a test and then the next day reverses those changes. The SERPs may also change slightly while they are doing other updating to the index. These are referred to as transient changes.
Transient changes are best seen when your page 1 ranking disappears without any reason and then the next day it comes back. If you lose your page 1 ranking, you should wait at least 1 day before panicking. If your ranking does not return after 24 hours, you might need to start your SEO efforts all over again.