I didn't charge my iPhone enough first time?

Now the battery doesn't last a day I got it yesterday and didn't charge it for 8 hours if I let the battery drain then charge right up for a good few hours will this improve my battery life?

Fairly simple my dear, follow these 5 steps to enjoy a better battery life!

1) Minimise your screen brightness, reduce the vibration level/ Sensitivity

2) Turn off anything like GPS, Wi-fi, Bluetooth, Auto Rotation (these eat your battery like hell!)

3) Drain your battery Completely out. ONCE you have followed step 1 and 2

4) Charge your battery from 20% as this will help to maintain a healthy function for your battery. WARNING! Only do this ONCE every month.

5) Use "Airplane mode" in remote designations or when you are abroad to save power.

P.S:

Also try charging your phone at least 2-3 days a week rather than full 7 days.

There are lots of different opinions on charging a battery. With these new lithium ion batteries that are used on new phones it really doesn't matter that you didn't charge before using phone. On the old batteries of years ago it was advisable to charge for 12 hours before use because they had a "memory effect" these new ones don't have that. You should never fully drain one tho it can shorten battery life and also take your phone a long time to reboot after its charged again. With a new phone put battery in and use until the battery is down to around 20% then charge till full. And simply repeat use phone and charge at 20%.it takes around 4 or 5 charges before your battery starts to hold its charge and work at at its best. If your doubtful about it then google "how to charge a mobile" you will see then that everyone has a different opinion.