I'd also like to add - personal information includes pictures of yourself. DO NOT post pictures of yourself in any open forum on the internet. The reason is many pictures could give information about yourself away to unfriendly members. Such as a school uniform, crest or sport uniform could give someone the information of what school you attend or what sport team you are on - giving them access to locations you will be and times you'll be there. A picture taken outside your house or school could do the same. The obvious is it will allow everyone to know what you look like. This in itself is usually not a danger, however it could be if combined with other info you've already given about yourself or info you give in the future about yourself.
Posting you'll be at Wonderland or CN Tower or Specific Mall tomorrow or a week from now is giving away too much information. Suggestions: tell your friends face to face and make plans that way or call them up on the phone. Forums are for chatting about tv shows, songs and other topics of interest without ever touching on personal information. Who you are, what school you go to, and where you live is none of their business!