当然是加ing.how about doing sth.比如：how about watching a movie tonight?今晚我们一起看电影如何?how about having dinner this evening?今晚一起晚饭怎么样呢?how about doing 表示建议.其中的about在这事介词词性,所以用ing.再比如；used to do sth和be used to doing,前者的to动词不定式,后者是介词所以用ing接.
how about＋动词的ing还是原形