SQL Server: Proper way to order by name -

i have query containing lines following:

select    b.lastname + ', ' + b.firstname tm 

currently use order tm in order sort, seems work.

however, in order right, can tell me correct way here order tm?

order tm,   order b.tm,   order b.lastname + ', ' + b.firstname  

or else?

also, can tell me if need put tm in single quotes?

it seems work without quotes want make sure right.

order tm 

best way!

order b.tm, 

no, tm not 1 of b's columns.

order b.lastname + ', ' + b.firstname 

can done, first alternative easier.

qutes required reserved words, , identifiers including strange characters (incl space).