Gluing up smaller boards to make a larger panel, like most tasks in woodworking, seems easier than it really is.
Lets say you need a panel that is 10" wide (the length does not matter at this point), and you have a 4 inch wide board to use to make this panel. You'll want to cut the 4" board so that you have three sections to edge glue together. This will give a slightly larger board than needed so that you can have enough scrap to square the panel after the glue up.
If possible, do not plane the boards to final thickness. If your planer is wide enough to accommodate the final board width, this is ideal. During the glue up, the boards may not align perfectly, and a board may glue up higher (or lower depending on which side you look at it). If one board glues up 1/16th higher, in this case you are loosing double the thickness of the height difference to make the panel flat again, 1/16th on both sides. If you were at final thickness before glue up, you must be extra careful for this.
Here's the first tricky part. You'll want the best looking panel possible, so you will have to rotate and flip the boards to get the best grain match you can. But at the same time, you will have to pay attention to the grain direction on the end of the board. You want to avoid having the growth rings turning all in the same way. Otherwise you may have trouble with the entire board cupping in that direction over time due to relative humidity changes. [Some woodworkers say that this is not necessary anymore due to our air conditioned and heated houses, but it doesn't hurt the process as long as you can get the desired final appearance of the panel]
After you've decided which boards you will use in what order and what faces are the good faces, the next step is to mark them somehow so that you can replace them the same way after you have machined them. The standard way that most woodworkers do this is to draw, with pencil, a triangle over all the boards. Not only does this method tell you the sequence and face of the board, it also indicates the position of the board relative to one another.
It is not neccesasry to use biscuits or any other joinery technique when gluing up wood panels edge to edge. This is one of the strongest wood-glue bonds.
Once you have your boards ready, try to get the glue up done that same day. Leave the boards sit for a long period of time and you will notice that your once perfect alignment is now out of whack due to humidity changes in the wood causing the boards to ever so slightly warp and twist.
When you are ready for glue up, get all of your clamps and cauls prepared on a flat surface. Do a dry run to make sure that everything will go smoothly.
Within your clamps, stand the boards on edge in their proper order. Glue up the boards by running a bead of glue (usually PVA glue is best for this application) over one edge of each board. I usually smooth it out with a small sponge roller to make sure the entire edge is covered. One at a time, lay them flat and start to align them properly.
You will notice that the glue acts like a lubricant and that the boards will have a tendency to slip out of place. One way to avoid this is is you own a pin brad nail gun is to put two pins into one edge of each board. Another way if you do not have pin nailer is to use a staple gun and cut off the flat part so that you have just the two tines of the staple slightly sticking out. This will keep the boards from slipping. I would only really recommend this method on larger panels with many boards as a safety precaution. Otherwise, a small glue up is probably managable without this alignment help.
Last step is to clamp your panel together. Using your caul, clamp the boards so that a line of glue squeezes out of each joint. You don't want to over do the pressure as it will cause too much glue to squeeze out, and your entire board may cup under the pressure and the clamps will trend to lift the tow outer boards.
After about 20 minutes (with PVA glue) you can remove them from the clamps. You can also take a cabinet scraper and scrape the glue off the joint if it is reasonably hardened. Let the panel sit overnight on a flat surface before working with it.