Google Trends can be used in a multiple ways to improve your SEO. A few such tips are here -
1. Set Variables
You can set four variables for searching for trending keywords. Set for
a) Search - Web, image, news, product and YouTube.
b) Choose specific country or worldwide.
c) Choose a time frame for search
d) Choose categories among various available.
2. Keyword Search
It will show you which keywords are better in connection with your business. Suppose you deal in automobile parts. You are confused between which keywords are better- auto parts or car parts? A search on Google trends makes your decisions easier.
3. Geo Tagging
Google trends will be much helpful in deciding the affinity of a keyword based on the region. A keyword popular in one may not be as popular in another. You can check which keyword sells in which area.