Trams take up a lot of roadspace, it should be restricted only to major thorough fares.
The better model to start out with is have wheels+spoke model of metro rail for inner city, radial commuter/suburban rail (to connect inner city to suburbia/satellites) and then a good bus system to interlink/refine this system where appropriate.
Paris is good case study for all (i.e RER vs Metro rail design + buses/trams on top only where appropriate). Trams are best once you reach certain equilibrium of the bus requirement AFTER heavy metro+commuter rail put into place...i.e you can start out with segregated BRT infra and convert them to street trams with time if appropriate. This helps in saving money and cost long term in creating less redundant tramways and the effects those would have on crowded streets in the interim.
@Mage