How do you know ...

[RubyRose]

If you've been successful at casting a circle or say a protective circle/bubble around yourself for protection?

[Xander67]

Belief, for starters,
and as long as you put your emotion into it.
and you amy feel a sense of ease, peace, security...

and visualisation is good too

[Demeter]

I don't know about other people, but I can sense it a number of ways.

If I'm watching a circle casting from outside, and close my eyes, I can "see" the barrier go up like a wall of light (I see it as a red energy usually, though that may just be because I'm seeing a white energy through my eyelids). With my mundane senses, I find that it is often hard to hear clearly what is going on inside the circle, even if I am so close that I ought to be able to hear it perfectly.

It's a little different from inside the circle, but if you extend your palm outward, you can feel a tingle between palm and circle wall, the same as when you are sensing a human's aura. If the circle is outdoors, sometimes you may notice that the breeze inside the circle is less than it should be, given the movements of plants outside the circle. And finally, at least with my group, it can get quite warm inside a circle; there is a noticeable difference in temperature as soon as the circle is released.

If you want to experiment, get a dowsing crystal or rods; you should be able to use them to determine where the actual edge of the circle is, and learn how to feel it.

[Rain Gnosis]

Most people in the beginning, in my experience, do not sense the circle at the outset. Many people just haven't been open to sensing energy (understandably), so don't worry if you can't feel it. For the first while just imagine it and believe it's there, and after some time you'll start sensing it physically (seeing or feeling it) too.

But really, don't feel odd if you can't sense it yet.

[Ahautenites]

I was a practicing Wiccan for four years and never once sensed the circle. I just understood that it was there. **shrugs** On the bright side, I can usually find people when I'm looking for them because of the tingling in my hands, so my spidey senses aren't totally broken. :)

[Carmelo]

I didn't get to feel the circle until my self-dedication ceremony. That night, while meditating with my eyes closed, I saw the circle through my eyelids. Turns out that I had made it with my power colors. Not long after seeing that, everything went dark again and then i could see a golden glow descending around me.

Seriously, don't worry about seeing or feeling it, yet. It will happen when you least expect it. Feel without feeling. See without seeing.;)

[Erincelt]

I've had circle castings where it was "almost-visible" as a light blue field of energy.. I've had castings where it appeared like a slight warp in the light.. I've had castings where it appeared in numerous other ways, or simply didn't at all. The Circle is pure energy, residing not in our physical realm but across realms, so don't be surprised if it isn't always apparent to the empereal (sp?) senses, ie touch, sight, hearing, smell, taste... It just is, and if you've cast with confidence, there's no need for verification: you will know.

[Jenett]

Different people perceive it differently.

Probably the most common one I know of is feeling it get warmer, or noticeably more or less windy (if you're outside or have windows open) once the circle goes up. The group I work with has a running comment about feeling the temperature drop once circle is opened - great in July and August, not so much fun in May or September when we're still outside, but it's likely to be bordering on chilly.

Sometimes people perceive a change in pressure around them, or a deadening of sounds outside the circle. Sometimes people can see the energy of the circle, or the sort of light-warping heat-wave effect (like if you look over the top of a radiator, or across pavement on a really hot day)