Troubleshooting:
Only feed your starter unbleached flour and unchlorinated water. It will not ferment and activate properly otherwise.
You will come to find out that temperature has a huge impact on sourdough. Keeping the starter at 75-85° F is ideal. Anything less and the starter will take longer to ferment. Some great options for warmer areas in your home are above the refrigerator, in the oven with the oven light on, or above a fireplace/heating vent.
If your starter is not starting to bubble and rise between feedings, try allowing the starter to set for an additional 12 hours to give it more time to ferment. (This is often needed when a starter is being kept at a lower temperature)
After a few days, your jar may become messy and hard to keep clean. Pour your starter into a clean jar every few feedings if needed.
The best starters are not necessarily the oldest starters. The best starters are the ones that are fed consistently. Feed your sourdough daily and accurately and you will be rewarded!