there is no taboo.you can say as follow:
周末准备干什么?/周末有什么计划吗?/周末有活动吗?等等
for the hat ,there is no taboo also,if he or she is your friend,you can say any words,even you can say your hat is disgraceful,terrible,bad-looking,if you do not know he or she well ,you had better say your hat is cool/good-looking or other praise words.bear in mind that there is no taboo between true friends . 对于帽子问题,如果不熟悉的话你可以说你的帽子很好看,很酷,很不错等,这样很保险,如果是很熟悉的朋友,你可以随便说啊,就算你说他帽子很难看,很傻,很幼稚。