I'm not sure about SM in the morning vs. evening. I always did hear about hot tubs and stuff. Just to be safe, I always ask DH not to take his showers right before. I've also heard that lying down for 10-20 minutes is good, but this past month, my doctor told me to DTD at night and go right to sleep....not to empty my bladder until morning. I was really afraid of UTI's, but thankfully, that didn't happen this month at all. Good luck.
ETA: Lots of girls have become pregnant though not lying down. Sometimes I think it just makes us feel better to stay still and give the boys a chance to get to where they need to be!! My doctor did tell me I didn't need to stand on my head or anything crazy like that

He knew I was feeling desperate!