Otherwise chances are high that you will get wrong results, because they must be used with care, and having an idea of what the result should be:
1) Beam element in a FE program is exactly the beam Euler-Bernoulli
2) Euler-Bernoulli theory is accurate for length-to-thickness ratios above 10, acceptable above 6
3) FE programs also have Timoshenko theory (including shear), which extends the validity to ratios of about 3-4. In those cases, FE also gives accurate results
4) If you use solid elements in bending take into account:
4.1) Linear elements lock in bending. Do not use squares, bricks, triangles, etc. Only squares and bricks have incompatible modes to alleviate locking, but are not good enough. Plates and shells suffer similar issues
4.2) Instead use quadratic elements: 9 node and 27 noded lagrangian elements. 8 node and 20 node elements are not the best choice, but acceptable.
4.3) Loads have to be introduced consistently (i.e. look at the shear distribution in a beam)