1) Do not buy on tips or rumours. Consult someone who has long experience of equity investment. (I consult linear or newbie or uncle sam in my chat box)
2) Do not buy with borrowed money. ( I borrowed from my daddy)
3) Do not buy shares in boom times when everybody is buying and sell in bust times when everybody is selling. Or put differently: do not buy when shares are at a high and sell when they are at a low - you will make a loss! ( Like dat, I should not sell now)
4) Do not invest in a share that has been in the spotlight recently - the price might already have been driven up significantly. ( Example:Supermax, Rubber stock)
5) Do not buy a share just because the price has dropped substantially and you think it is a bargain. There might be sound reasons why it has dropped. ( LCL, Etitech etc...)