Search engines always take into account the title text and keywords used in the URL of a web page while determining rankings of that page in search results. The influence may be small but keywords mentioned in the URL do carry some weight.
For instance, if all other factors remain same, a web page at abc.com/iphone-review may rank higher for a search query "iPhone review" than, say, xyz.com/best-phone or xyz.com/apple-phone-review because of the keyword iPhone that’s present in the URL.
*Most blogging platforms allow you to write custom URLs (aka post slugs in WordPress). If you are on Blogger, read this hack on how to create your own permalinks.
Now if you’re keen to master the art of writing good URLs that are descriptive and search friendly but without getting into any black hat SEO tricks like keyword stuffing, follow the style of Matt Cutts. He generally uses descriptive titles for blog posts but his URLs are short, neatly written and use only relevant keywords. Some examples:
Title: I do not wish my screensaver to lock my computer, thank you.
Title: Get your search fix with two videos
Title: Protect yourself: get a free credit report
Title: How to back up your Gmail on Linux in four easy steps
Title: How to stop junk mail
Title: I love my pedometer
Title: Crap. My Ubuntu machine won’t boot
Title: What are the best iPhone applications?
The above list is pretty self explanatory and may have given you a good idea but let’s just walk through the important points:
1. Search engines generally ignore common words like "the", "a", "are", "is", "of", etc – your URLs will therefore do just fine without them.
2. Phrases like "How to do this" or "Which is the best" or "What are the options" or "When did this happen" make titles attractive but you need not put these words in the URL.
For instance, Matt is using the URL "best-iphone-application" for a page titled "What are the best iPhone Applications." In another example, the url is "stop-junk-mail" for the article "How to Stop Junk Mail."
3. If something important doesn’t fit in the page title, put it in the URL. For instance, the URL of a page titled "Get your search fix with two videos" is like "free-search-seo-video" – so you have two new words ("free" and "seo") in the URL that were not in the title but do help in describing the underlying web page.
4. Use hyphens (or dashes) to separate keywords in URLs though Google can now also read underscores.
Google probably assigns some fixed weight to your URLs which gets distributed across different words used in that URL. Now the weight per keyword will obviously dilute when you have long URLs.
Therefore, it will help if you can manually create URLs with lesser number of keywords but they should also be relevant to the context of your content. It requires a little extra effort at the time of writing your blog post but the may reap good benefits in the long run.