1. Have two start times
If your venue's imposing a strict start time or time limit, it might be prudent to have two start times. By that, I mean put the start time on your invitations about 10 to 15 minutes before the actual ceremony time. This ensures a slight buffer time for guests who may be running late. The slight time difference also means you won't have to let guests who are actually on time, wait too long for the ceremony to begin.
See also: things to include in your wedding invites.
2. Be strict about it
Singaporean wedding banquets tend to start slightly later than usual, and with that, guests usually turn up later than the stipulated time on the invite. Prevent that by including a line at the bottom of your invite that lunch or dinner will start on time, and that the doors will close after 10 to 15 minutes. With that, you'll also have to convey clear instructions to the banquet staff that lunch or dinner will have to start strictly on time. On the day of, have your wedding coordinator remind the staff again.
3. Convey the message via your RSVPs
Reinforce the message when guests RSVP, or when you're chasing for RSVPs. With the former, thank them when you receive their response, and remind them again that the ceremony and reception will start at the stipulated time.
4. Remind your family and wedding party during the rehearsals
It's important that the key parties arrive on time. Your ceremony and/or dinner rehearsal's a good time to remind them to do so.
See also: tips on planning your wedding timeline.
5. Arrange for transportation
Do this only if your venue's located at a place which is hard to reach via public transport. Do note also, that transportation may get expensive, especially if you are planning for a large wedding.