Great idea! Always work on safe numbers HITs. There are a few batches that we all can suggest if needed. They are somewhat valuable for unlocking more HITs, although the impact of this is a lot less than most new Turkers realize... The more valuable thing is that numbers HITs help buffer you against rejections, allowing you to maintain a >99% approval rate, which is a really important thing to do.
Are you using MTurk Suite yet? It makes finding HITs so much easier regardless of what time you log-in for newer Turkers.
My general observations about timing:
1. Weekdays are when more surveys tend to be posted, and the frequency of new surveys being posted is highest during typical normal hours (8AM-6PMish EST). Being on the West Coast, I've found requesters tend to start slowing down a bit after 3PM in my time zone.
2. Weekends are always much slower than weekdays. Can't give an exact number but 75% slower sounds right. That being said, while there are fewer HITs and surveys posted, there are also far fewer people Turking on the weekends. Therefore, there's less competition. When I was really new and inefficient about catching HITs, I actually made more on weekend days than weekdays (However, I do have a regular 9-5 job that I work around on week days)
3. On weekends, I tend to leave Pandas (or Watchers in Hit Catcher) running for higher-$ HITs while I go do other stuff around the house. Last night, I left Watchers running for three >$5.00 HITs that others had posted on the forum earlier in the day. I gave my kids their baths and put them to sleep, and when I returned to my computer around 9PM I had caught 2 of those >$5.00 HITs. It doesn't always work-out so well, but in general it's not a bad idea to leave a 2 to 3 Watchers running while you're away from you computer.
Feel free to let us know if you have any other questions. Today is painfully slow... so people are probably more likely to answer since we're not preoccupied with working on tons of HITs.