Nami is my favorite supporter with great skills to help the whole team. In my opinion the best support. Her Q is a awesome cage and easy to hit on alot of adcs. Her W is a great heal and poke skill with a little training you can destroy the support and adc all by yourself. Your E is a great buff for your adc or any other ally. Your R is a great engage and awesome start for a fight. Your passive makes all your skills buffs too!

When you start don't instantly skill your W maybe you will need your Q in a early fight.
When on lane use your W to poke the enemy and heal yourself at the same time. Try to hit them both if you use it on the ADC try to stay near him and don't worry about the damage he could do since you will heal yourself. On lvl 3 if you hit your Q use your E on your ADC so he can get into the fight faster and deal more damage. After he took some damage heal him if you use W right you will heal yourself too. Auto Attack them to get some money from your spellthief's edge and do great poke.

This is what you wanna do the whole game. Take one enemy out with your Q and then just buff your team with W and E. If he doesn't dies and a team fight starts your R will make your team win the fight.

Don't forget to always ward at the dragon and in a bush if you are top side only use the second ward if you push if you are bot side always ward the bush over the bot the first tower.