When you should use a 301

[mikesonu]

You should also use a 301 if you have expired content on your website such as old terms and conditions, old products or news items which are no longer relevant and of no use to your users. There are a few things to bear in mind though when removing old content from your website -

Check your analytics to see if the content gets any search traffic, if it does, do you mind potentially losing that traffic if you remove the content?
Is there another page on the site which has very similar content that you could send the user to? If so, use a 301 and point it to the similar page so that you stand a chance of retaining the traffic you already get
Is the content likely to become useful in the future? For example if you have an ecommerce site and want to remove a product that you no longer sell, is there a chance of it coming back at any point?

[bruceruler]

You should use a 301 redirect when you send traffic to your site and want to keep their rank and authority of the place. We recommend using 302 or 307 redirect when you send traffic away from the area, but still want to keep the page rank and power.

[jackcalara]

301 is very useful for redirect your traffic.

[stacey]

When ever delete the page from the server it good to do 301 redirection to relevant page in the website. So, that we will not loose the traffic for the website.