Some tips:

1 - to list with line number from a single line, e.g. 10, up to the bottom line type: n,10,
2 - to list with line number the 1st 10 lines type: 1,,n
3 - to list with line number the previous 5 lines of a single line, e.g. 10, type: a,10,,p
4 - to scroll with line number 40 lines every time type: m,,n
5 - to search the string "string" type: s,string
6 - to delete it in any line type: s,string,
7 - to delete it in a single line, e.g. 1, type: s,string,,1
8 - to delete it in a range, e.g. from 1 to 10, type: s,string,,1,10
9 - to delete the last 10 lines type: d,-10,-1
10 - to convert correctly a text file from DOS/Mac to Unix format type o and then: s,.$,
11 - to save correctly a file in DOS/Mac format type o just before writting it
12 - the special form |cM is for a comma, so to search the string "string," type: s,string|cM

and so, take a look to Lua patterns.