Impressionante é derivado de dwm, certo? No dwm, você adicionaria 'regras' para certos programas (por padrão, há uma regra para o gimp e o firefox na origem do dwm).
Parece que é o mesmo para o incrível-wm também.
Você pode adicionar regras correspondentes à tabela awful.rules.rules. O padrão rc.lua já tem vários exemplos, mas aqui estão mais alguns:
-- Set Firefox to always map on tag number 2 of screen 1
{ rule = { class = "Firefox" }, properties = {tag = tags[1][2]}},
-- Set Smplayer to tag 4 of screen 1
{ rule = { class = "Smplayer" }, properties = {tag = tags[1][4]}},
-- Set Emacs to tag 5 of screen 2
{ rule = { class = "Emacs", instance = "emacs" }, properties = {tag = tags[2][5]}},
-- Set Alpine to tag 6 of the last screen
{ rule = { name = "Alpine" }, properties = {tag = tags[screen.count()][6]}},
-- Set Akregator to tag 8 of the last screen and add a titlebar trough callback
{ rule = { class = "Akregator" },properties = {tag = tags[screen.count()][8]}, callback = awful.titlebar.add},
-- Set Xterm to multiple tags on screen 1
{ rule = { class = "XTerm" }, callback = function(c) c:tags({tags[1][5], tags[1][6]}) end},
-- Set ROX-Filer to tag 2 of the currently selected and active screen
{ rule = { class = "ROX-Filer" }, callback = function(c) awful.client.movetotag(tags[mouse.screen][2], c) end},
-- Set ROX-Filer to tag 8 on screen 1 and switch to that tag imidiatelly
{ rule = { class = "ROX-Filer" }, properties = { tag = tags[1][8], switchtotag = true } }
-- Set Geeqie to the currently focused tag, as floating
{ rule = { instance = "geeqie" }, properties = {floating = true}},
-- Set Xterm as floating with a fixed position
{ rule = { class = "XTerm" }, properties = {floating = true}, callback = function(c) c:geometry({x=0, y=0}) end},