Invest into something you understand.
It is easy to get pulled into foreign stocks, foreign real-estate, close-end ufnds, low-price stocks, market hypes, penny stocks, options, futures, golds, bonds, junk bonds, tax-free securities, real estate, spread betting, neighbour's business, commodities, lottery, pilot games, etc.
The basic idea is this: there are always opportunities.
Do you really understand the area you are getting into? If the answer is no, you should not!