Depending where you're flying, some arrivals have gaps which threw me off massively when I first started - it's because IRL there's ATC there to guide you to the final intersection for the runway, usually 10NM out... so aim for that and capture ILS, it's quite a wide margin for capture.
If you're going manually, 10nm out you want to start descending at around 600-700fpm from ~3000ft and you should have visual on the runway at this point