You don't need to do this when purchasing a DSLR.
When you get the DSLR, it has probably around 40% charge because that's the optimal charge for long-term storage. If that partial 40% charge doesn't annoy you, you can start shooting immediately. Or, you can charge it immediately if you want to.
DSLR lithium-ion batteries are unlike car lead-acid batteries, they like operation at partial charge. So, actually charging the battery to full reduces its lifetime! So, you get slightly better battery lifetime if you start using it immediately and then charge when the red low charge indicator blinks. But you get only 40% of an additional cycle for free, with battery lifetimes being around 500 cycles, so the benefit in starting to use it immediately without charging are minimal.
To avoid battery problems, you should avoid elevated temperatures at 100% charge. Most laptop batteries spend most of their time at elevated temperatures and at near 100% charge, and they last only a few years. DSLRs do not heat up naturally as much as laptops do, so the only thing you need to keep in mind is to not leave a 100% charged battery in a hot car. Try to avoid storing batteries in freezing temperatures as well. Electric cars have in-built battery heating systems, DSLRs don't.
Also, try to avoid charging obsession (charge to 100%, use until 90% charge left, charge to 100%, use until 90% charge left, ...). So, don't recharge all the time, recharge only when you have used a sizable fraction of the battery capacity (not necessarily draining it to completely empty, as partial cycling may have benefits). The reason is that charging damages batteries the most if it's nearly empty or nearly full*. Try to prefer charging whenever you see the red low charge indicator blinking, instead of using every last percent of the battery charge.
If you need to store a battery for a long amount of time, charge or deplete it to approximately 40% charge level, put it to a plastic sealed ziploc bag, and store it in a refrigerator.
The charging is fully automatic. It will show when it's full and there's no need to leave it in the charger for a longer amount of time. No damage either if you forget the battery in the charger.
With these tips, I'm sure you'll have many useful years of battery operation.
* sources / justifications: