Vim: Search for What You Select

Way 1:

1. yank the selected text with y
2. go to search mode /
3. paste the last yanked text with Ctrl+R 0

Way 2:

1. yank the selected text with y
2. go to search mode with command-line window q/
3. paste p (and you can continue editing)

Source: Search for selection in Vim - Stack Overflow