Keep it.in the fridge. A few days (usually 1-4 days) before brew day get it out and leave it to come up to room/pitching temp slowly then smack the pack and leave to expand (if wyeast) before pitching it into a starter culture. Depending on what you're making and age of the yeast you may need to make a starter - a low gravity ale should be fine pitched direct but anything much over 1040, or a cool fermentation like a lager, will need more yeast. A starter will take a day or two to build up before pitching - lots of info on making these up with a little DME and a good habit, you can also split the starter and save some split sections for future brews to culture up into starters which then makes liquid yeast cheaper than dried as well as better.
And none of this is a complicated, nor essential, as it may sound - but all good stuff to try out and learn.
What's the yeast, when was it made what are your plans for it?
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