Get your IDP from the official issuing body in your home country before you travel. That is typically the national automobile association or the government transport office, never a website promising instant international licenses, which are worthless. The process is usually simple: application form, passport photos, your valid license, and a modest fee, often done same-day at a counter or within a couple of weeks by mail.
The 1949 versus 1968 convention question trips people up. Countries recognize the IDP issued under the convention they signed, and the two documents have different validity periods, with the 1949 version generally valid for one year and the 1968 version for up to three years, though never beyond your underlying license expiry. Some countries accept only one type, so check which convention your destination follows before applying, since some issuing offices can produce either.
Remember the IDP is only valid together with your actual license, so carry both. And it cannot legitimately be issued or renewed while you are already abroad in most cases, so this belongs on the pre-departure checklist along with visas and insurance.