Open file
vi filename
As i am newb on linux macine, i dont know vi shortcuts.
so, i am listing down shortcuts which i am getting familier. :)

Insert in file
i

Exit file
q

forced exit
q!

save file
wq

forced save
wq!

Copy no of lines
yy

Paste copied lines
pp

Undo changes
uu

Delete lines
dd

To search and replace string in vi
:%s/search_string/replacement_string/g

To find particular word in file
?string1

If you have any quick list. please, let me know