So many things can affect a recipe, here are some that most beginners run into:
1) measuring flour -- flour can be "compacted" so if you spoon flour into a measuring cup and scrape flat the excess, you will have around 4.25-ounces of flour (this is the recommended procedure of most recipes); BUT, if you scoop your measuring cup into the flour and flatten the top by pressing down the flour, you may have a 6-ounce cup of flour, or nearly 30% more than a recipe calls for! This will make a very dense bread, even though it seems like you are following the exact same recipe.
2) water temperature -- most machines compensate for too cold of water, but cold water may not activate the yeast, and the bread may not rise as well by the final rise. On the other hand, too hot of water simply kills yeast. You don't need a thermometer, aim for warm to touch water, like warm baby-milk -- if it is too hot to you, it is definitely too hot for the yeast.
3) yeast and salt -- should be around 1/2 teaspoon each per cup of flour
4) oil and sweetener (not artificial sweeteners) -- around 1 tablespoon per cup of flour is a general rule of thumb. Artificial sweeteners should be less than that. Solid shortening and lard can be much more, but not butter (it melts at too low a temperature, so treat it as a liquid oil)
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Consider measuring by weight, especially if you already have a kitchen scale that is precise to 1g or 2g or 0.1-ounce. You have to find recipes written this way (lots on the internet) or convert them (also easy to do). This is much more consistent than using cups.
Also, a good idea is to perfect a basic bread recipe, so you know your bread machine, then venture out. Basic means flour, water, salt, yeast (often described as "french bread", but a loaf of this is nothing like a proper baguette) :-)
Hope this helps...