What are some special care I must take while writing my scientific simulation suit using C++ (read c++11)?

I use a combination of SystemC, SystemC-AMS & C++ to model architecture and proving the concept. I am very curious to receive opinion from others. I use lot of GNU GSL. I care for speed and I address multi-physics & mixed-signal systems with lot of signal processing (both analog and digital). I am expecting expert tips here.