Lord-bearing walls help support the weight of the house by removing a load-bearing wall and replacing it with a beam; it is very different from removing interior non-load bearing walls. Non-load bearing walls also known as partition walls are there simply to divide space (not to support loads from above).
If your thinking about removing a load-bearing wall there is lots to consider:
DIY - This is quite a heavy project so most homeowners would consider hiring a contractor but it is possible to do it yourself. You must pass inspections and must adhere to the local building code requirements (just like a builder would). You will also need to check with your local permitting authority or building department for guidance.
Permits - Most projects will require a permit and inspection eg. Wiring and plumbing upgrades, structural changes, fences, decks, load-bearing wall removal, walkways, ponds.
Your permit agency always needs to know if you are taking down a wall, as it affects the structural integrity of your home. Large walls require an architect's drawing and an engineer's stamp of approval.
If you remove a wall it must be structurally replaced. When you or a contractor remove a load-bearing wall, it must be replaced with either:
Beam: A horizontal structural beam of sufficient structural quality must replace the wall.
Beam and post: A horizontal beam that has one or more intermediate posts between the two end bearing points is also an acceptable replacement.
Consider a LVL Beam For Better Support - Laminated Veneer Lumber (LVL) beam is an improvement. LVLs create better strength in a smaller space rather than similarly sized dimensional lumber. A four by six inch LVL will be much more powerful than a single piece of four by six dimensional lumber. Fortunately LVLs are not that expensive, only architectural LVLs are and that is because the wood is meant to be seen not covered up with drywall.
A Replacement Beam will be lower than the ceiling, so the floor structure above can sit on top of the beam. Intervening vertical posts under a carrying beam do take away from that perfect open floor plan look. However any kind of vertical support you can add under a horizontal beam will give your beam assembly for better strength.
Beam Sizing - When sizing beams there are several factors to take into account such as deadweight vs live weight, roof loads, deflection and shear. A structural engineer or contractor can consult with you on the proper size of the beam.
Using temporary supports - Prior to removing any part of a load-bearing wall's framing, you must build a temporary support wall on both sides of the load-bearing wall, so that the floor joists above may have their ends sitting on the load-bearing wall. If you add temporary support on only one side of the wall, the joists on the other side will not be supported.
Structural Beams - Successfully built structures are constructed with redundancy in mind. Imagine after a tornado or earthquake, where two-story houses have exterior walls ripped out yet the building remains standing, the reason is redundancy. However, gravity will slowly take over and the house will begin to collapse. This is a reminder that you should not be lulled by the power of structural redundancy. Gravity will always win.