A way to make it slightly less work is to use a cell reference in the countif formula. So, for example, if you were trying to count the appearances of your letters in cells A1:A10, you could list your four values (A,B,C,D) in a column (say, d1,d2,d3,d4.) In cell e1 put the formula =countif($a$1:$a$10,d1). This will count the A's, as d1 has an A in it. Use fill down and the four totals will appear. Probably not worth the effort for counting four items, but definitely a time saver if you wanted to count a lot of different things!
The other approach is to use a pivot table - use the wizard, it's really easy, let's say that your column of letters had the heading 'Letters', put 'count of letters' as the data in your pivot table and 'letters' as the column heading.
Are you in education? I use this all the time to count up grade totals!