The simplest answer and the one that no student that ever wants to hear is practice. Changing chords is the process where many beginners fail, and quit. But after that, the rewards will be simply impressive. There are a few tricks to get a chord transition to happen faster. Use a metronome: Set it on four beats and set it as fast or as slow as you want. Then get a chord in your mind, say D. When the metronome reaches its last beat, press down the strings. When it happens again, strum it and let it free. Then again. Do this 10 to 20 minutes a day and in less than a week, the chord progression will begin to sound much better.
Practice fretting the strings. The frets are the metal strips that run perpendicular to the strings that mark each note. To play a note, press your finger down between the metal strips, not on them. To say that you're playing the third fret means that you place your finger on the string in the gap between the second and third fret. If you hear buzzing, move your finger away from the lowest fret and closer to the higher fret. Hold the string down firmly so that it only vibrates between your finger and your strumming hand, with the tip of your finger doing the pressing.
Hold your guitar correctly. When you are sitting down, there are two main ways to hold your guitar. For a casual playing style, lay the guitar over your dominant leg. On the other hand, the classical method has you set your guitar on your non-dominant leg. In both instances, make sure that the guitar is held close against your body. Holding your guitar properly makes it easier to play and prevents you from becoming fatigued. Play around with both styles and figure out which one is most comfortable for you.
Learn the difference between chords and single notes. Chords occur when you play two or more notes on different strings simultaneously to create one unified sound. These are what make up the "rhythm" portion of acoustic music. Single notes are used more for solos and occur when you play a single note at a time. Both are skills that you must become proficient in when learning to play the acoustic guitar.
Beginning Guitar Class - Open to all beginners age 13 and up, or intermediate players who want the review. Begins with holding and tuning your guitar, names of guitar parts, and quickly progresses to chords, scales, tabulature, and playing basic songs. A variety of styles are introduced to encourage students to explore and find the styles they like best. Classes are organized according to age and skill level, so it's an easy way to make new friends too. Classes start every month and may be repeated as often as you like. Cost is $70 per month (4 hours).