Once you know your basic 7th chords (Maj7, dominant 7, m7, m7b5, dim7) Most of the alterations occur in the dominant 7 chord (1 - 3- 5- b7). In reality only two notes can be altered. The 3 can become a 4 (for the x7 sus 4) and the 5 can become #5 or b5. If you alter the 1, you are starting on a new root and therefore a new chord family. If you alter the 7, you are changing the chord quality. And any alteration of the third, OTHER THAN the sus4, (i.e. to b3) changes to a minor quality. So, a chord that is, say C7#5 simply means to raise the 5 one-half step. and a C7b5 simply means to lower the 5 one-half step. Important note: in chords, the # and b signs mean to raise or lower the step that naturally occurs in the chord. Thus a B7 #5 is B D# F##(or G) A. A B7 b5 is B D# F(natural) A (not an F0b or E).
Your next step is to learn all of the extensions -- 9, 11, 13 -- as they naturally occur in the chord scale. Thus a C 9,11,13 (C13) is C E G Bb D F A. A B 9,11,13 (B13) is B D# F# A C# E G#. A "#" with any of these numbers means to RAISE that chord member one-half step, and a "b" means to lower that by one-half step. In a C7 #9, the D becomes D#. In the B7 #9, the C# becomes C## (same as D). A C7 b9, the D becomes Db. A B7 b9, the C# becomes C natural.
Basically, you are just "following the instructions." Find the chord as it would be without alterations (C7 #5, #9 -- find the C7, 9 or C9 chord then follow the instructions for raising the indicated chord members.)
A C7 #5,#9 is C E G# Bb D#. A B7 #5,#9 is B D# F##(G) A C##(D). A # anything (#1, #4, #5, #9, #11) means to raise that chord member one-half from the member that naturally occurs (#4 -- often indicated +4, does occur in some jazz charts). A b anything (b1, b5, b9, b13) means to lower that chord member.
Note, there is no b11 (same as the major 3rd) and there is no #13 (same as the b7).
Here are the basic 7th qualities and the most standard alterations and tensions (9, 11, 13).
Major 7 -- #5, 9, #11, 13
dominant 7 -- sus4, sus2, #4 or b5, #5, b9, 9, #9, 11, #11, 13 -- a b13 is occasionally seen. It is the same as #5
minor 7 -- 9, 11, occasionally 13 or b13.
m7b5 -- 9, occasionally b9
diminished 7 -- 9, occasionally b9
note a #9 is the same as the minor 3rd so it would be redundant in any of the minor chords.
The major 7 does generally not use natural 11 because the tritone between the 7 and the 11 has the effect of creating a (9), 11, 13 chord with the 5 as root. CMaj7 11 -- C E G B D F = G7 (9), 11,13 -- G B D G (A) C E