The single largest tip is to never exceed your budget regardless of how good it looks. If you have a credit card, put it in a drawer for emergency cash. It isn't even permissable to use for emergency cash. When buying a car, buy a used car and base the purchase on price, safety, fuel efficiency and repair history of the model. Rarely pay down a mortgage and refinance the rate down when possible. Only use fixed rate instruments unless you are certain you are going to move away in a reasonably short period. Never buy a house as an investment, always buy it as a dwelling. If you were already rich and understood the dynamics of your real estate market, then consider investing in real estate, but real estate investing in some ways requires greater sophistication than stock investing.
As one realtor who also invests described to me, if you don't have a hundred units, you don't have enough to be diversified or profitable on a regular basis. He is right. Most little landlords don't really make money when opportunity costs are considered.
Be conservative in borrowing money. You are using someone else's capital and that is good, but be conservative. Worst case scenarios happen.
In equity securities, learn to do financial statement analysis and do it well. Do not invest yourself until you do. Until then, if you are in the US, go to Edward Jones. They are expensive but they are good and they will keep you out of mischief.
Finally, 80% of the people who drive cars believe they are better than the average driver. Of course only 50% can be and there isn't any evidence the 20% who do not think they are, are in fact the best drivers. The average investor believes he or she is much better at it than they are. PRESUME you are an inferior investor. This will help you tremendously, especially if you actually get good. Do not select investments you like, this is the path to destruction, exclude investments you do not like. You will find a set you are uncomfortable with but cannot find anything wrong with. This is probably the best set. It is rare for an excellent investor to really be comfortable with their investment set.
Use objective criteria based upon fundamentals alone and begin excluding choices. Include the entire universe of investments including debt instruments.
Finally, there is a 50% chance of you becoming disabled for at least three years and a 33% chance of dying before 65 so two other tips. Your most valuable asset is you, so buy disability insurance...very good disability insurance. You will find not all policies are equal. Little differences have big consequences in terms. And, if you plan to marry then buy your life insurance now, it is cheap. Shop around too. The difference over long periods of time between the best and worst policies can be 6x the outcome. If you happen to be Catholic consider the Knights of Columbus, their whole life policies, because they do not pay taxes, come in just slightly below the bond market rates. In essence they act like very strong bond market mutual funds with super low fees.
Finally, learn to use Excel.