As far as i understand the runic formulas work in the manner of bindrunes, collecting the energies of the runes for a collective effect. For example the formula ALU (Ansuz-lagaz-uruz) has been used a lot historically for magical power inspiration and energy.
The book Operative runology (ALU) by Thorsson goes into depth on magical formulas.
I have written some basic information about how they work here
Personally, I feel that people should do personal study into each rune by spending time with the energy/spirit of each, as well as having a thorough understanding of the Havamal before attempting to use runes in magick. By understanding the morals and values of the Norse people, you learn the way the runes will behave and why.
For instance, gebo means gift. But what is a gift? A gift to you may not have the same meaning as a gift to the ancient Norse people. In the Havamal (which has many translations online)
"A man must be a friend
to his friend
and give gift for gift.
Men should use
mockery in return for mockery,
and deception in return for a lie."
"One should not give a man
a single large gift:
often one can obtain for oneself with a little praise:
with half a loaf
and with a sloping goblet
I got myself a comrade."
"It is better that it be not invoked
the gift is always for the repayment,
it is better that it be not sent
So with this in mind, you can see that the Norse did not see a gift as given with no strings attached. A gift was owed some form of return but EQUAL return. When using the runes, and especially when using them to gain something, you must remember this.
A gift for a gift.
You have to be willing to put out what you receive and it won't always be your choice as to what you're giving. I do notice that this occurs most often when the runes are not stained and no offering (sacrifice) is given up front. I've observed people that ignore the need to give experience "backfire" and in my opinion, it's due to them applying their own ideals and expecting the runes to bend to them. They don't take into consideration the ethics surrounding the runes.
I read the Havamal like I'm getting to know a person. As I read it, a personality develops and I apply this to my view of the behavior of the runes when I utilize them in magick. And I have never once experienced an unpleasant result.