I have taught a lot of people to knit toe-up socks and one concern which comes up time and again is the issue of getting a good fit around the heel. If you are used to knitting your socks from the cuff down it can take a while to adjust to the toe-up mindset and how a heel is constructed.
When you are knitting from the cuff down you don't really need to think too hard about heel placement. You knit down the leg until it is long enough then you knit the heel and as you work your way down the foot you can slip it on as needed to check where the toe decreases start.
With toe-up socks you need to be a bit more precise about where the heel placement is and I think this is where many new toe-up knitters suffer from a lack of confidence.
What I suggest, for a standard short row heel, is to start the heel once the finished sock is the total length of your foot minus 2.5". One thing that it is important though is that when you are measuring the sock length you stretch it really quite firmly. It's no use taking the measurement on an unstretched sock as you need a degree of negative ease. No one wants a baggy heel. The fabric needs to have negative ease so it will cradle the heel and give a good fit.
The problem is that if you are unusued to knitting this way the foot looks disproportionately short and knitters lack confidence in 'going for it'. So, to achieve the the perfect heel fit try the following:
1. Try the sock on as you go.
2. Knit until the firmly stretched sock reaches a point 2.5" away from the back of your heel.
3. Put in a lifeline (just in case of freak accident)
4. Work your heel
5. Knit a few rows up the leg and then try on again
If it has all gone to pot then your lifeline is there waiting to save you but 9 times out of 10 these simple steps will work. Depending on foot anatomy you may have to adjust the crucial 2.5" measurement (if someone has a particularly high instep, for example) but this would be the case with cuff down socks as well.
As with all these sock tips do let me know if you've tried them out, and more crucially, whether they worked for you.