I guess bridges may not be considered "safe" but they work.
If you are worried about hurting yourself start with front bridges-they are the safest, in my opinion. They are also the easiest.
Form? Changing your form will help streanghten the muscles. Once you feel more comfortable in the exercise feel free to arch your neck diferently. Simply searching the internet will help you find a form you are comfortable with enough to start with.
When I was a wrestler we often rocked up and down and rolled between front and back bridges.
When I first started no one explained the form, you just did it-while that is not really a good argument for just doing them, my point is that I've never heard of anyone hurting themselves doing bridges.
The best part? Bridges are FREE.
p.s. this is probably common sense but just in case - do them on a padded surface like carpeting or a mat.