There Are Pandas, and Then There Are Pandas.
And this isn't either of them! The Pandas we're talking about here, are watches, not bears. And what got me thinking about them (again) was a link posted this morning by @cm.rook who pointed a few of us to the very attractive (and not terribly priced) Yema "Rallygraph" Panda which, in it's most traditional arrangement, looks like the one on the left, but can also be had in the version on the right: The model on the left is a true Panda, while the model on the right is called a reverse Panda. The reason for that distinction is clear--Panda bears, only come in the first arrangement. Now at this point, everyone should be thinking about the most well-know Panda, The Rolex Panda, which is actually a Daytona, and among Rolex Daytonas, the most famous of which is the Paul Newman Daytona, which was famous first, because it was Paul's, and second because it sold at auction for $17.8 million (US Dollars). The story of that auction is well-known so I'll only...
Nov 8, 2019
One important thing is to make sure you develop good gluten structure in the dough too. A technique called the stretch and fold can help do this with higher hydration doughs. Also the advice below of "Poke with your finger. As soon as it stops springing back it's ready." is a great place to start for knowing when it is ready to bake.
When troubleshooting, it's important to understand why bread turns out the way it does. Wheat flour contains two key proteins -- glutenin and gliadin. When the flour is lubricated with a liquid, like the water in our bread recipe, the proteins slide around and link together, forming long, stretchy strands. The more water your dough has, the easier it is for the proteins to move around.
But just adding water isn't enough. Gluten requires some outside force to help develop and arrange those chained together proteins into the cell network that bread requires. Two processes contribute to this. The first, is yeast. As yeast eats the sugars in your bread dough, converting them to carbon dioxide and alcohols (which improve the flavor of your bread), it also works to develop gluten. The other process is kneading. By stretching the gluten strands and folding them back on themselves, you organize them into regular, evenly sized cells. The ratio of how much you knead to how much you let the dough rise will depend on the result you're looking for. Sandwich loaves should have a regular, relatively small cell structure, and most of the gluten development should be done via kneading. Artisan loaves should have a large, irregular cell structure, and so most of the development should be achieved via yeast and rising time.
If your bread is dense, I expect you didn't have enough water in your recipe. The gluten proteins won't have enough lubrication to fully develop. Without developed gluten, the cell structure can't form. Without the cell structure, the steam and CO2 from the yeast won't be able to make the dough rise. So yeah, more water. Also, I recommend using bread flour. It has a higher gluten content than AP.
Bakers often use the term "hydration" when talking about the ratio of water to flour. Specifically, hydration is the ratio of water to flour by weight. Bakers use weight to measure everything because flour is inconsistent. Its density can vary by batch, and the only way to make sure you're using the same amount of flour every time is to weigh it. As a starting amount, I recommend 60-65% hydration. That is, if your recipe calls for 350 grams of bread flour, then you should be using 210-230 grams of water.
Personally, I prefer higher hydration. In my standard loaves, I'll do 70-75%, and in more artisan, crusty loaves closer to 80-85%. Hydration impacts everything from oven spring, to crumb texture.
To avoid adding too much flour when kneading: Some people recommend oiling your hands and work surface to avoid over flouring. I don't like this method, because fats inhibit the formation of gluten and can change the texture of your dough. Instead, stick to flour. Dough should be kneaded with quick, confident motions. The faster you move, the less the dough will stick to your hands. Flour your surface and hands lightly -- as much as you need to but no more. Within a few minutes of kneading, the dough should be developed enough to not need any flour, because the gluten will be more interested in sticking to itself than to anything else. Really, the best tip I have is confidence and speed.
Have any changes you've made made a difference?
By saying "simple bread," I am going to assume the ingredients are only flour, water, salt, and yeast. I am also going to assume you are making an "artisan bread," since a "lighter, softer bread" with just those ingredients can be a bit difficult.
Most of the replies given to you will help. I just wanted to add on that even before you make your dough, you can make a starter. This will ensure that your flour is as hydrated as it can get, which will vastly change your outcome than adding in flour or water during or after mixing, which should be for very small adjustments depending on the environment, not for tweaking. Here is random site on two common starters: http://www.weekendbakery.com/posts/more-artisan-bread-baking-tips-poolish-biga/
Also, just wondering, did you check your yeast? I apologize if you already know, but a reminder that yeast is a living thing and will go flat. Here is random site on how to check your yeast: https://www.thekitchn.com/active-dry-instant-yeast-best-tips-for-working-with-yeast-180312
Additionally, the temperature of your water can and will alter your dough (and your yeast). Dense means that your dough may be too cold (should be around 72F out of the mixer) and/or isn't proofing enough.
Finally, although it is difficult to do at home, artisan breads need steam to fully leaven and develop a crust. This can be done by making your starting oven temperature higher than on the recipe, then spraying water onto the dough.
Anyways, it's best to post your recipe at the very least since there are so many things that can alter your result, and usually its a combination of things instead of just one issue.