Statistical analysis indicates that orange is only a small percentage better than green but way easier to acquire.

Ranking;

Orange

Green

Blue

Light blue and purple

Yellow and red

Railroads

First 2 cheap properties

Utilities are usually only worth the mortgage value. Never pay full price for a utility. Not even to keep it out of acompetitor's portfolio.

Hotels are usually a waste unless it's just to end the game quicker. Winning move with upgrades is 3 houses unless adding the 4th will limit other players ability to build because of not enough houses. Yes, the total number of houses is limited, and yes, that's part of game's strategy.

Never allow a competitor to acquire a monopoly without securing one for yourself.

As soon as you acquire a monopoly, mortgage everything to start building.

Analyze every trade by looking at what each party has left to build with moving forward, not the dollar value being put into the trade by each party.