Planning

I think that sites provided by governments and from professors or university students are more reliable because they are people who are publishing work to contribute tot he learning of people all around the world. They aren't people who are waiting for money as a return or such a thing.
Doing a regular google search will give you information anyone can publish even if it is wrong. Therefore doing a google advance search will provide you will some solid information which is CORRECT (depending on what site of course). Books or online encyclopedia are better to use than a search engine because they are books that have been gone over many times and correct/proof read/pre-viewed/edited many times.
It is also important to know who and when the information was published, because if a teenager published a certain information he/she will have a totally different point of view compared to an adult. If a certain information was published in a certain year (such as the year a certain natural disaster occurred) it will be different aspect to read about it when it occurred than to read about it now that 10 years, or such, passed by.