by default database are usually set to autogrow anyway. you may want to check this setting and confirm the growth factors are something sensible (50 - 100Mb usually good but is dependant on current database size).

If you know the size you want the database to be then growing it to that size in one chunk is the best way, but if you have the disk capacity and there is a chance of sudden unexpected growth then leaving autogrowth turned on is a good idea. Better to have the database grow a bit then run out of space.