There has been some debate recently about whether tactical voting is possible to influence the list vote in May's general election. It isn't.
If you want a Yes MSP, you should vote for the National party on your first vote, except in Glasgow, Kelvin where you have a choice between the National and Green parties.
On the List, you should vote for the party of your choice. If you want an SNP government, you ought to vote for your top-up MSPs to come as far as possible from the Nationalists. If you want a pro-independence majority, but are loath to give the SNP another majority, you might lend your second vote to the Greens or any other pro-independence party.
This, of course, carries the risk that your vote doesn't count in the final reckoning of seats.
A foolproof way to ensure that an SNP which wins almost every constituency can maximise the number of pro-Independence MSPs returned from the List would be for them to stand down from the List and recommend a vote for the Greens. This would ensure the Yes vote is not split, but also would vastly reduce the effect of the SNP's victory in constituencies by sharply reducing the applicable divisor in each round.
For my own part, I will be voting National at constituency level (with quite a heavy heart, as I am registered to vote in a constituency with an able and dedicated Scottish Labour MSP who I feel should be a loss to our politics if she was out of Parliament, and I would not be at all upset if she retained her seat. However, my vote for the National party in my constituency will be conditional on the candidate supporting the repeal of the Offensive Behaviour &c. Act in the V. Parliament) and I will be voting Green on the List in the hope that a victorious National party will not have an outright majority, and will be unable to promulgate poor legislation of the type regrettably passed without proper scrutiny by the IV. Parliament.
Majority government inevitably produces arrogant government without the need to seek consensus, and produces bad law. I will discuss this in greater depth as the campaign progresses. However, in the meantime, be in no doubt: unless the unlikely happens and the SNP pulls out of the List, it is fundamentally impossible to game an AMS system in which the list votes are cast before constituency results are known.
If you want an SNP government, you won't get it by voting Green, or Lolidarity, or for the Transcendal Meditation Goat Party.