A few minutes before the scheduled start is usually best. Give yourself enough time so you are ready to start the meeting bang on time. If you spend a few minutes getting yourself organised at the start of the meeting, it'll give the impression of being late, even if you arrived on time.
Don't forget to check any joining instructions - they may help you decide when to arrive, for example if refreshments are scheduled before the meeting, it gives you a wider time-window for arrival.
You do need to be aware of the culture, particularly if you're not familiar with the other attendees. Being a few minutes early gives you the opportunity for personal introductions in advance of the meeting.
Also, in some organisations, arriving on time is equated with being late.
If the culture is for everyone to arrive late for meetings, it's still advisable to be a bit early - just in case that particular meeting bucks the trend and starts on time.