(1) Being Consistent with a schedule- Being consistent with having your toddler on a schedule is on of the ways to have your toddler take a nap at the same time everyday. Toddlers are extremely smart so once you have them on a schedule they will start to know the schedule everyday and will have to remind you one day of the next thing to do on the schedule. If you are sitter or nanny, it will help them build trust with that toddler as well.
(2) Outdoor time- Outdoor time will tire a toddler out to where they won't have energy sometimes to eat lunch, but this technique works, take the toddler outside for about 1 1/2 hours a day at the same time, and bring them back in for lunch this will help so much, you will see a big difference in the toddler falling asleep faster and staying asleep for at least 1-2 hours everyday.
(3) Have lunch before nap- Having lunch in addition to outdoor time is really important because once you come in from outdoor time, and have lunch, your toddler will be tired and full! Great combination. Try this and see it work wonders!
I will post a great schedule below that I have used at my daycare for years and it works!
7am-8am-Breakfast, after breakfast help with potty training or bathroom time
8:00am-9:00am-free play time in playroom or play with toys
9:00am-10:00am-Do something educational such as singing songs, tracing letters, learning number, etc
10:00am-10:30am-Have a snack
10:30am-Noon- Outdoor time, tired them out with different fun activities
Noon-12:45pm-Lunch, after lunch empty their bladder if potty training
12:45pm- 2:30pm, nap time, play some lullaby music on Pandora
Your toddler or child will sleep like a baby and you will have the best break of your life for these 2 hours.
REMEMBER TO STAY ON THIS SCHEDULE AN BE CONSISTENT!