Below are the possible factors will affect your salary:

1. Job Area
2. Company Industry - Oil & Gas higher, Banking Industry good bonus, IT industry work late.
3. Locations - SG, KL better, If you work at Kelantan might be not so good.
4. Experiences, Skill set: IT line: Most of .NET/Java programmer get higher salary than Ruby/PHP (open source) programmer.
Sales people: your past experience, earn how much for your companies through sales.. etc.
5. Qualification - for fresh graduate education tend to be important, diploma, bachelor degree, Master -> all make differents.
6. Type of company: MNC, china man company, local company, oversea company, home solo business.
7. Languages: Know good English will make different if you are working at MNC or company that required English for their business, For china man company who have business in china of course Chinese Languages tend to be more important.
8. Your interview: Good interview will make different.