A Few Tips to Help Maximize Practice Time
Control your environment. It really helps to be uninterrupted. Let family and others in your household know that you need focused time. Select a space that is away from the fray of daily life: a basement room, or on a different floor of the house.
Keep the space tidy. A cluttered space can result in a cluttered mind. If you spend the first ten minutes of your supposed practice time just trying to find your instrument under piles of clothes, books, and paper, you will not come to your practice session with an uncluttered mind.
Practice when no one's home, or when no one else is awake. You'll know you're not interrupting anyone else, and you'll be free to make your own mistakes without worry of someone hearing you. It also allows you to take risks or try new things that you might not have tried if you knew someone were listening. If you can, sound proof your room.
Secure the support of those you need most, whether it be your close friends, your spouse, or your partner. Let them know that daily practice is important to you. If it really is that important to you, you'll find that you're a far more pleasant person to be around when you're doing it. The rewards will be obvious both to you and to those around you.
On that note, no matter how important practice is, take care of your family first. Your practice will have much greater chances of success if it is in balance with the rest of your family life. If you are skipping the family dinner in order to practice, you may find that family or your partner resents your efforts, and as a result, any efforts you make will be counterbalanced with the work you have to do to right your relationship.
Turn off the phone. Calls can wait 'til you're done. It's too easy for a phone call to completely derail your practice session.
Take your time. Especially when your practice time is limited, remember that it's quantity over quality. Better to spend 20 minutes working out that two-measure bug in a tune you've been learning than to rush through all ten songs that you're trying to keep current.
Play slowly. Better to play a tune once or twice, but do it right, than to play it twenty times but repeat the same mistakes. Playing slowly also exposes your weak points. You'll quickly see which parts of the tune you don't really know, when you force yourself to play a tune very slowly.
Remain focused. Don't phone it in. Especially once you're getting to know your tunes well, or when you're working on one of your daily practice routines (such as playing long tones), it's easy to tune out and not pay attention. You may find that you've been playing for ten minutes and not heard a single note you've played... instead, you were thinking about your to-do list for later in the day, the guy who pissed you off in the grocery store line, or the car repairs you haven't yet scheduled.