When taking up surfing, one of the first dilemmas beginners are faced with is to know what type of surfboard is best suited to them. The good news is that there are surfboards particularly well adapted for beginners and ideal to learn to surf: the so-called mini-malibu (aka Mini-Mal) or evolutive boards.
These surfboards, collectively known as funboards, allow for an easier and smoother initiation, with great buoyancy and stability (for easier paddling and better balance), as well as a good level of maneuverability to enable you to make your first turns and tricks. Granted, their shapes aren't as cool as those of the pro surfers' boards, but they're without the shadow of a doubt much more effective when first learning how to surf. One of the typical newbie mistakes is to try to learn to surf with a shortboard, which is normally better suited to surfers with some experience, but not at all to beginners. It's much easier to learn the basics of surfing on a big, large board than it is on a small board because the larger board's buoyancy and stability makes it a lot easier for a newbie to paddle, stand up and take waves from the very first day.
In a nutshell, surfboards for beginners should be much longer, wider and broader than the average shortboard. As a rule of thumb, a beginner's board should usually be 15 to 25 inches longer than his/her height. This way, it's very easy to know at first glance whether a surfboard is suitable for you by just standing beside it. The longer and wider the board, the easier it'll be to stand up but the harder it'll be to turn and maneuver. This is why you shouldn't pick an excessively long board either just because it'll be easier to stand up. So you have to find a good compromise and 15 to 25 inches longer than your height is in most cases a good approximation.
Many surfboard brands offer mini-malibu or evolutive boards in different sizes and slightly different shapes to meet every surfer's need. Obviously, you can go to a surf shop to buy a brand new board and/or get a "shaper" to make you a customized surfboard according to your skill level, height, weight and the type of waves you'll be surfing. But you should also take into account that when a surfer has acquired sufficient experience and skills, s/he'll usually buy a shortboard (or a "shorter" board), which means that there's a fairly active second-hand market for mini-malibu or evolutive boards in surf shops, surf schools and on web forums. If you are on a low budget, this is a good option, but beware of surfboards with cracks, dings or DIY botched repair jobs and make sure you check the offer price against brand new boards with the same characteristics. Using a second-hand, inexpensive surfboard or a borrowed one (going to a surf school for example) until you've been surfing regularly for at least six months is often recommended as beginners tend to put a lot of wear and tear on their first board.
Once you'll have clocked a fair amount of time taking waves and reached a better level, you'll probably want to "swap" your board for a smaller one. By that time, the experience acquired should help you have a better idea of what kind of surfboard is best suited to your wants and needs.