There are several methods:
1. Setting the search to be case insensitive in Vim
To unset it:
You can also put it to your .vimrc if you want the behavior to be the default one.
2. You can also force a patten to be case insensitive or sensitive by
\C regardless the setting of
For example, the search
/dog\c is always case insensitive. And
/dog/C is always case sensitive.
To enable it:
If your search pattern is purely lowercase, it will search case insensitively.
If your search pattern contains uppercase characters, it will search case sensitively.