Set realistic goals and a realistic time limit to achieve that goal! 30 minutes to 1 hour is a GREAT amount of time as a beginner to start practicing. As you learn more and encounter harder music, you might find that you'll need a little extra time to achieve your practice goal... and that's ok!
Be sure you're utilizing your practice time to the best of your ability! For your set amount of practice time, put away anything that might distract you (cell phones, video games, computers, etc.) so you can focus 100% on the task at hand. You'll find that when you really focus, you'll get more done in LESS time!
Consistency is key! Ideally, EVERY DAY PRACTICE will help you solidify and remember what you've learned! However, because we are all busy people, sometimes that just can't happen. If you find that you can't practice every single day, aim for 3-4 days per week!