European Nucleotide Archive is good place to start to download the raw fastq files. But it is not easy to download multiple run files from NCBI SRA database. I recently learn to download in relatively easy way. I want to download these four run together from NCBI SRA database : SRR122247,SRR122248,SRR122249, SRR122250. Format of basic url is like that

ftp://ftp-trace.ncbi.nih.gov/sra/sra-instant/reads/ByRun/sra/{SRR|ERR|DRR}/<first 6 characters of accession>/<accession>/<accession>.sra

Where {SRR|ERR|DRR} should be either ‘SRR’, ‘ERR’, or ‘DRR’ and should match the prefix of the target .sra file Described in details HERE. So my final urls will look like this

ftp://ftp-trace.ncbi.nih.gov/sra/sra-instant/reads/ByRun/sra/SRR/SRR122/SRR122247/SRR122247.sra
ftp://ftp-trace.ncbi.nih.gov/sra/sra-instant/reads/ByRun/sra/SRR/SRR122/SRR122248/SRR122248.sra
ftp://ftp-trace.ncbi.nih.gov/sra/sra-instant/reads/ByRun/sra/SRR/SRR122/SRR122249/SRR122249.sra
ftp://ftp-trace.ncbi.nih.gov/sra/sra-instant/reads/ByRun/sra/SRR/SRR122/SRR122250/SRR122250.sra

Now save this urls in a text file (url_list.txt, for example). Run the wget like this

wget -i url_list.txt

run sudo apt-get install wget from terminal if you don't have wget