Give it a couple of days, THEN worry. One day isn’t always enough to see krauesen or bubbling airlocks. It will most likely start just fine in the next 24 hours. But if not, you should always have a pack of dry yeast on hand for such emergencies. Unlike liquid yeast, dry yeast will keep in your refrigerator for many years and does not require a yeast starter. Speaking of which…
You should also always make a yeast starter with liquid yeast, especially with White Labs. With Wyeast, you can get away with smacking the pack to wake up the yeast and ensure the pack swells up in a few hours. If it doesn’t swell quickly, then you need to make a yeast starter. But with White Labs, you can’t smack anything to start them out so you need to wake up the yeast manually about a day in advance by mixing a cup of DME in ~2 cups water, bring to a boil, and cool and pitch the yeast into this small yeast starter batch, just to get them moving before pitching into the big daddy 5-gallon brew.
Following these simple guidelines will ensure fast starts every time.