I went out last Saturday en femme for the first time. I was meeting some people in a LGBT friendly part of town I had never been in, at a very busy bar that i had never been to, which was quite an ambitious undertaking for the first time out (i'm bigender and my girl mode has a lot more brass than boy mode has LOL....). There were moments of sheer terror (like after i parked the car but before i got out, when i started thinking too much about what i was doing), and when i had to walk two blocks to the bar - past a sidewalk cafe - in heels. You feel like every eye is watching you (the "spotlight" effect), and you start second guessing what you are doing.
Once I realized that no one was in fact watching me i was able to relax and enjoy the evening. No one said anything and i didn't catch anyone leering at me. I was just a girl out for a nice evening with friends. After an hour i had almost forgotten that i was dressed fully as a woman and I was just having fun.
My suggestion is to think of scenarios where you'll feel safe and start out exploring those. Remember the safety rules for girls too - no walking alone at night, stay in well lit areas, hang onto your purse and keep it zipped up, etc.