Buckle up! LOL
My biggest pet peeve is woman focusing on body parts in Male written fiction. Men are obsessed with 'size'. Her 34D breasts, his 8 inch penis etc. Women don't give a shit about size in that way. Looking in the mirror is fine, as @Bad_Princess says, most of us have a love/hate relationship with it, but saying something like 'she admired her 34D breasts' rings totally false. If you must go expository more than having someone ELSE admire her 'large shapely breasts' along the lines of 'Dan watched Mary stroll by on her way to work. "God she's got great tits, especially for someone so thin," he thought to himself. "Those things have to be at least a C cup." then work it in some other way, like she's upset that her bra doesn't fit the same anymore. "I've always been a 34C," she thought to herself, "but I'm spilling out of these cups. Damn it, I must be putting on weight."
Women tend to be holistic in their approach to looking at themselves or others and are more likely to obsess on self-perceived flaws than to 'admire' their own features.
As for checking out guys, it's the same. We're not going see a guy nude and go "OMG his cock has to be 10 inches!", we're going to say, "Mary stared at Ken's erection, her eyes widening. It was the largest cock she had ever seen." More likely we don't give a shit over his cock size as long as it's within the bell-curve of average and doesn't look diseased. We're likely to call a well-formed cock 'beautiful' as opposed to 'huge' or 'powerful' or something. Women tend to focus on face, shoulders, chest, hands/arms and bums more than cocks anyway. I don't speak for all women but if you're looking to write fiction from a woman's POV keep the above in mind. There are plenty of women who are 'cock watchers' but honestly, as a male author, you're safer writing characters that 'aren't'. You'll be less likely to make her a dude with a pussy and tits.