Wall paper removal can be tricky. Non-toxic removal techniques include using a steamer (rent or buy) and/or removal solutions.
What works for you project will depend on a variety of factors including:
- the type of wall paper,
- the type of glue used and
- the age of the wall paper installation.
It has been literally decades since I removed wall paper from a wall, but I used a steamer. The steamer had hit and miss success. In some sections of the wall it worked like a charm but in others it damaged the sheet rock paper (requiring a complete replacement of the sheetrock). My technique was probably a bit flawed at the time. It is best to start at a corner and pull the paper back at a 45 degree angle.
In the event you would prefer a solution approach, try mixing two parts white vinegar with warm water and apply the solution directly to the paper with a sponge or rag in an effort to dissolve the glue. Using a putty knife, peel back the paper with the glue, use the putty knife at a 45 degree angle to remove any additional glue.
If you find your results are not adequate, you could consider trying a commercial removal solution such as Simple Strip. I have not personally used this product so this is not an endorsement.