^ If you are feeling impatient you could dissolve a 1/4 bar under your tongue, let it dissolve and you will be able to guage effects quicker to decide if you want/need to redose. I will warn you that xanax tastes quite bad sublingually.
There are many people sensitive to benzodiazepines who will get knocked around by small doses, but there are equally many not so sensitive. While I would be surprised if you felt no appreciable effects from .25mg I would be equally surprised if you found it a sufficient recreational dose. Best to start slow though because you can always take more.
From my personal experience when I wasn't tolerant to benzodiazepines at all I wouldn't notice any appreciable effects till abot .5-1mg and generally considered 1.5-2mg an optimal recreational dose.
Xanax is very non toxic and generally requires ridiculously large doses to cause death if it is being used on its own, but it causes blackouts very easily which can cause some unruly and regrettable behaviour which, more often than not, lands you up shit creek in one way or another.
It would be wise to avoid alcohol for the first time using a benzodiazepine, particularly a stronger one like xanax. If you feel you must indulge I suggest you do not exceed more than a few (2-4 YMMV) standard drinks. Benzo's mixed with alcohol can cause blackouts and unruly behaviour ridiculously easily.
I am not sure if you indulge in Mary Jane but personally I find excellent synergy between these two substances. If you overdo one or both you can expect strong sedative effects, although this is a fairly safe combination overall. I find it best to take a slightly larger than therapeutic dose of benzo and then smoke what you normally would to get stoned, without going overboard. It leads to a very relaxing and anxiety free stone that I think most long term smokers would appreciate greatly.